Actually, LA, I negotiate often as part of my job. The problem is, and I learned early on in my career, that sometimes you don't deal from a position of strength. At that point, you make the move you have to make in order to get what you need. It is better to overpay and actually have what you need, than to not pay at all and have nothing.
At this point in time, there are very few quality LT options available to the Bills. We are starting a rookie QB. We just lost our starting LT to FA. Our O was called out by our GM and blamed for a non-playoff season.
Conversely, from Arizona's perspective, there are plenty of options at RB. Arizona is actually dealing from a position of strength here. Not us.
Therefore, in my opinion, it is better to overpay within reason (4-5th rd pick) and have a starting quality LT, than to have no LT at all. You can overplay your hand when negotiating and TD may do it this time.