It is not important whether those users are newbies or experienced but not really good at dealing...
The prices of players should not vary to much between selling and buying.
With (of course) the exception on whether they had been trained.
When I'm writing "should not be varied", I mean that the variation should be small (10-20% top, and should not be a way of making big money).
This game is about BB-managing, and not about BB-agent, or BB-eBay.
And thanks to you and Manouche, we have a proof for WallyOop, who claimed that there aren't cases like that...