I think you are off the mark in saying the Sabre is way better built. I am familiar with those very fine boats, but i think quality here is comprable.
What do you know about the Nassau?
I am surprised at that price for an Irwin. In my area, I have seen better built boats from that era (like C&C, Ericson and Endeavor) asking around 22K or less. the boats around my area are fresh water, including the one I just bought, and they do stay in better shape because of that.
The surveyor I used is one I have used before. He is well known in my area and has an excellent reputation. He usually is pretty critical, but was very favorable to this boat, its construction, and condition (including those teak decks).
BUC can be very misleading. Since only about 15 of these boats were built, the sale of one can make a big difference in the BUC rating.
Judging from boats in my area, and having looked for quite sometime, I obviously felt this price was fair or I would not have agreed to it.
I guess you experts see things differently.