Am I missing some unspoken rule?

The key word in trading is profit.

Their bundled price should be about equal - 5 games in a 3$ bundle ends up each costing 0.6$. I don't know what you would consider fair - obviously for example Batman AA was bundled, but still worth more than let's say... Lucius. It's just better. But nowherenear it's full price, but rather in a 1-2$ range, if it comes to trading.
Afterall, if you feel like the trade is unfair, you can always counter-offer or decline the trade, just make sure that you're rejecting a truly onesided offer.

There are a lot of people who are only trading to profit - so you will always get a lot of low offers (especially games that were given away for free). As long as you aren't being unreasonable then you will eventually get the trades you want - but you may need to be patient, there aren't always people there right away with the games you want who also want your games.

being in bundle already means losing value. if game you have and game you want has been in bundle, trade shouldn't be hard. if you mean that, for example, you're bundle game is worth $15 and you want game worth the same, it won't happen if you're game has been in bundle and other one haven't. even with bundle game being much more expensive than non-bundle game in store, for example, will most likely not succeed in trade

If you're getting in to trading, of course you're going to be approached by vast numbers of people trying to take advantage of you to gain a profit from trades, offering higher number of low value games etc. It's up to you to determine whether the trade is to your benefit or not. Never accept a trade that you have doubts do, do your research on current market values, and continue to follow your instinct like you are. If you're not close friends with someone offering you a trade, expect them to be trying to get the upper hand on a deal. You're more than likely right, the majority of the time, people will indeed be trying to rip you off. That's just something you'll have to continue to identify.

That sort of thing is common in nearly every trade forum, there'll be always people trying to made awful deals like trading copies of 15 cent games for CS keys 1:1 or random throwaway bundle games for the latest fotm 60$ game
Just keep an eye out for like minded people who are also up to reasonable trades, and you'll eventually find some good deals

Steam is full of kids. Noone with real understanding of actual life. Sure you trade for profit, but they take it too far and think they can trade a hand full of warm shit for a chunk of gold. All those people want to trade 1:2 or even 1:3 while trading 1:1 when they want something.
Don't go with lowballers! It takes time but there are decent traders out there!

some people love using store prices for their bundles and bundled prices for others' games :3

like putting together 20 bundled keys worth $3 and trading it for an arkham knight gift. "hey, all these games together are worth $260 in the steam store!"

If you have low rep people will asume you're new to trading, and there are many traders trying to make a profit by ripping off newbs.
Just by patient, and keep looking.

not that your actual logic is flawed at all but your want list compared to your have list is quite a bit one sided.. i'd guess roughly 75% of your want list is higher value never bundled games (or higher tier bundled) versus 100% of your have list is bundle spares.. seems you will accept most fair offers of bundle 4 bundle games too though from reading thru the comments, but it might just be a little bit of a deterrent for some people to see that kind of want list they dont even bother with fair offers..

I bought a four pack of Screen Cheat before it was part of the recent Humble Bundle. I CONSTANTLY had people trying to offer me games that Indiegala gave away for free for a copy of the game. A lot of people here either dont have or choose to ignore the concept of value. Offers like that I just politely reject and wait for something better to come along. SC getting bundled hurt me a bit, I'm likely not going to be able to get what I wanted for those when I first bought the four pack, but so it goes. Eventually a fair offer will come up and both me and the other party will be happy

I don't think you should complain.
You just tried to lowball me: 4 of my games for 3 of yours (bundled games).

This is why I don't trade. I have spent only about $300 for my ~500 game library plus a lot of DLCs and all of it was either through the profit received from farming cards, free games given by websites, winnings from here, a few bundle purchases, and many on sale on Steam. Way less stress and I don't end up with a bunch of unwanted junk unless it's from a bundle that I had only wanted a game or two out of. I have seen too many people getting ripped of by "reputable" traders and it's just not worth the grief and effort to me.

I've tried trading a few times, and I still intend to get some games that are missing from my library with trades in the future, but you should definitely expect people to try and take advantage of others, especially strangers on the internet they will never meet in person. That's not to say there aren't some truly golden traders here; one especially memorable trader was kind enough to point out that some of the games I was requesting from him were available for purchase in a very cheap bundle on DIG. The trade was definitely in his favor, and yet he decided not to take advantage of me when he had the opportunity. I thanked him for the information, thought about it for a day, and went through with the trade anyway because of his honesty. But that was a one-time event for me. I haven't traded many times on this forum, but for the one time that someone was honest to the point of almost hurting themselves in a trade, there have been (at least) three times that people have taken advantage of my lack of knowledge and/or pressured me into a trade that was unfair to me. I obsessed about those losses for a while, but ultimately, they were valuable learning experiences.

Take your time to consider a trade, and don't let someone else pressure you into making a decision before you are ready. Websites like Is There Any Deal? are invaluable tools for making a decision that's fair to everyone. Don't be afraid to say "No" to a trade, and don't be afraid to make a counter-offer if you think the trade is unfair. And try to make sure that any offers, counter-offers, and agreements are clear, explicit, and made on the trading forum here or on some other public forum on the internet, and not just through Steam chat. I haven't had anyone renege on an agreement, fortunately, but I have made deals with people through Steam chat, and then took the time to make sure that the agreement was copied to the trade forums on this site (with both people posting their agreement), so there was a public record of the agreement in case the other party ever did renege, and I needed to leave negative feedback that could be supported with evidence. That hasn't happened to me yet, and I hope it never does, but it's better to plan for the worst while still hoping for the best.

It depends on what you consider as the value. Steam store price? Bundle price divivded to the number of games? Overall length and quality of the game? Or a sum of this factors with added coefficients? And don't forget to take rarity and average ref/cards price among traders into consideration.

So yes, I also value some games from my H-list more than the others and want some games of my W-list less than others, but I don't try to pretend there's some universal objective value scale. If you like the trade offered then do it. If you don't - refuse or ask to add something.

Also a good idea is to make a realistic wishlist in your thread (no AAA/unbundled games there). And don't count too much on bulk trades - generally, it is pretty rare to find a person interested in even one of your games while having at least one game you need at the same time.

That's how trading works.

9 lowballs in every 10 trade offers, 8 of them are probably Russians. Russians make no sense in anything in this world.

Note that, RARITY of being in a bundle of the game and BTA price affects the real value of the game. Like some guy said earlier, Batman AA was bundled ONCE and is a great game so it worths a lot more than normal bundle games. But for example, Mechanic Escape was bundled a lot and even given away for free everywhere so it doesn't worth anything at all.

I'm only going to add one thing to this conversation. When you DO find a decent trader, one who is fair and straightforward with you, make sure you keep track of them. A circle of good traders is invaluable because you have specific people you know will deal with you fairly. After a couple of years, I now have trader friends in most regions. This allows me to check with someone to see what is fair market price, and whether a deal sounds good or not.