If they can pay then so be it, I'd probably do it if someone paid me but this is straying away from the original point of trading and payments over trading which is a different concept. Paying someone to run a bounty is probably very rare and a fairly long process. This has it's own risks in exchanging profile information etc. This is a persons own risk rather than Bungies. Having a trading system which would more than likely encourage people to use real money to effectively buy weapons would be both a risk to the player and Bungie. If someone pays a person for a gun but then that trade fails to happen then how much of an head ache would that be for Bungie? This would open up a can of worms that would be difficult to contain.