I trade/sell only by the steam non-sale value of the game(s) you want. I will also only take money through paypal since it what I use and have already, never even heard of the others nor would I get another cash app or whatever just for one deal and likely never use again.
So for example, if you want a 19.99 game off me, you pay 19.99 through paypal or trade me a game or games also equal to 19.99 since I only trade value for equal value since bundles games can not be calculated equally easily, if at all. Better to just treat every game as if someone paid the full price for them. Don't like my buy/sell or trading method, then do not deal/trade with me; it's that simple.