That shouldn't be the case. But here you go https://steamcommunity.com/tradeoffer/new/?partner=54524730&token=t2gt4tOI

I'd prefer the skins reaching equal or atleast 85% value of the game you'd want.
Mobile authenticated trades take priority.
Available game trades:
-Castle Crashers €12
-Another Zombie Defense €2
-Darknes II €30
-Gun Monkeys €4.5
I'll also make other trades if the offer is reasonable.