why are the case keys in cs:go higher valued at market than the in game market??

In order to access the CS:GO market, you need to actually own the game whereas TF and DotA are free.

cuz market takes some $ when ure selling something?

Because 1. People seem to buy them a lot (crazy?) and 2. Steam adds a fee to the price of goods sold in marketplace.

buying like 20 csgo keys in game to after sell them on the market makes benefit of 1€ for example, maybe ppl who are buying from the market don't own the game.