I wonder what happen to just plain old player trades? Aka, join same server lobby, invite to trade or drop on the floor to show the stat and then specifically agree to give to another player in a trading window.

Right, the devs gets nil in this type of transaction, even though it could really help players engaged.

I can almost guarantee that if a dev include a "tip the developer" option(no dark pattern, basically you buy some premium credit and use it as tip with minimum amount like a quarter), people would be guilt tripped to the moon and have to press that button once in a while. (Basically like the wikipedia funding request, I got guilt tripped easily. )