Mind you, I'm new to this scene but I have experience in shoes and small model trading which have similarities. Based on what I've seen watching this place, it's a very fine line but there IS a difference between flipping for cash and trading for an item of higher value. I know on paper the end result appears the same and in some specific instances like this, it would be.
But that extra step/layer of the second person receiving goods (instead of cash) keeps the floodgates closed on outright flipping for cash, which is bad for what /r/mm is trying to accomplish. You guys are so much better than most trading forum because of this. Sure, people will do these sales behind the scenes anyway but with a growing market/hobby the last thing we need are outsiders seeing easy dollar signs, coming in just to flip caps OPENLY. The easier it is, the more it will happen.
As trivial as that extra step seems (allowing goods of same value vs. frowning on cash), it's the only barrier we have before this place turns into every other expensive, limited product hobby out there. It seems hypocritical on paper but the line has to be drawn somewhere and in the absence of a better idea, this appears to be it.