Are games worth current price or original price in giveaways?

Giveaway point costs are based on original price, so there will be no changes whether the game in question is on sale or not

Prices doesn't change unless base value changes on Steam. Sales and promotions are irrelevant. Also from FAQ this is how giveaways work.

What are "No Value", "Reduced Value", and "Full Value" giveaways? How do they affect my overall contributor value?
When creating a giveaway and selecting a game, you'll notice "No Value" games are marked with a double asterisk (*), and "Reduced Value" games with a single asterisk (). If you hover over those icons, you'll see the effective date for the value adjustments. For example, if a game is marked with a single asterisk (*), and hovering the icon shows "Reduced value since January 4, 2018", this would mean giveaways created for that game on January 4, 2018 or later will receive reduced contributor value. Games typically receive no value or reduced value when they're featured in bundles, heavily discounted, or available for free in online promotions. Their values are adjusted this way to better represent their true value. Keep in mind, the asterisk icons are just for reference, and the value of a game can be backdated if we need to make retroactive changes.
Games fall into one of the below three categories.
No Value:
No contributor value when given away after the effective date.
Reduced Value
15% contributor value when given away after the effective date.
Full Value
100% contributor value when given away.
If you visit your profile, you can see a breakdown of your previous giveaways. If you hover over the "Gifts Sent" number on your profile, you'll see the number of gifts you have given away in each category.
For example, you give away three games. Game A is $10.00 and it has no value. Game B is $20.00, and it has reduced value. Game C is $50.00 on Steam, and it has full value. Once your giveaways have ended and the gifts have been received by their winners, you will see the updated values on your profile. In this case, you would see "Gifts Sent: 3 ($80.00)". This would show that you have successfully given away 3 gifts, and their current list price on Steam is $80.00 in total. If you hover over the number of gifts, you would see you have one "No Value" gift, one "Reduced Value", and one "Full Value". If you hover over the dollar value, you would see you have a contributor value of $53. It would be calculated as 0% of the gift with no value (0 x $10.00 = $0.00) + 15% of the gift with reduced value (0.15 x $20.00 = $3.00) + 100% of the gift with full value ($50.00).

Thanks guys!