But what about the green trust which is given for reasons like-
[bought a X, he sent me first, paid later]
[Escrowed for him]
[Sold a Y, he paid first]
How much weight does this feedback carry?
It's up to the reader to decide how to value feedback. But indeed, instead of "buying" (with a almost certain risk of getting scammed) feedback for $40, doing an actual trade can be a much cheaper way to get green trust.