I think I was unnecessarily unclear - let's say we're talking about buying eggs. Suppose I'm willing to pay up to $3 for a dozen. That doesn't mean that I should buy them if I find eggs for $2.99 - I should keep shopping around, because grocers can profitably sell eggs for $2 a dozen, so I'm bound to find eggs closer to the $2 mark. I need to take into account what would be reasonable for the other party when deciding if a deal is reasonable, not just the limits of what would be reasonable for me. If I'm stuck, and everyone is selling eggs for $3 a dozen, then it matters whether that's beyond my personal threshold or not. If I only note how close a deal is to my personal threshold, without noting whether the other party would be likely to agree to a more favorable deal, I'm liable to get ripped off, unless I have no leverage for negotiating anyway, and I can only take it or leave it.