If Bob is willing to pay $x.xx for something, and Fred is willing to accept $x.xx to give up that something... then who are we to step in and tell Bob:
Oh, no, I realize you're willing to pay that much for it, but if Fred isn't willing to take less than that, then we will force you to keep your money instead of buying it.
And who are we to say to Fred:
Oh, no, Fred... I realize you're willing to give this thing for only that amount of money, but if Bill isn't willing to give more than that, then we will prevent you from selling it. You will have to keep that thing that you want to give to him and go without that money that Bill wants to hand over to you.
This is a private relationship between two people, and as long as they aren't breaking a legitimate law -- e.g. selling stolen goods, selling something under fraudulent terms -- then no one has the right or authority to step in and tell them both that they can't do it.
Note, this also applies to labor and the minimum wage.
:up:
Matthew 20
He is usuing his parables again about the Kingdom, but still an accurate economic lesson.