I agree that, unless an examination of the gun supports the price, $800 is very high and even worse if it does not include the buyers vig. That being said, if you really want the gun and are able to do so, I would not fault you in the least for paying the price for it. I don't believe in belittling a person's gun because I think he or she paid too much for it nor would I want anyone to not share their gun with me because I or someone else makes them feel guilty for paying, and being able to pay, a higher price for the gun than the generally accepted prevailing market value for the gun at the time.
Reported prices for guns are what a willing buyer chose to pay a willing seller for the gun at the time. The transaction depends on the parties' respective circumstances at the time and is not always repeatable. Auction prices can even be more deceptive. I see a gun sold at an auction and naturally think that it establishes the fair value. Of course this is wrong. It only means nobody at the auction wanted that gun more at the time its lot came up for bid (generally a small universe of buyers). If I had been there and wanted the gun it would have sold for a higher price.
Another consideration with less encountered guns, such a high condition pre-War or early post-War Terrier, is that you don't see them that often and when you do they are often high priced. So if you want one you face a low probability of finding one and the the low probability of getting one at a good price before somebody else buys it. There is nothing wrong with accepting the odds and waiting until you find one at a "good" price. Judging from your posts, many of you choose or have to do this.. But there is nothing about being a good collector that requires you to not only find and buy a good gun, but also to get it a "good" price. I don't think that there is anything wrong with paying the price you are required to pa for the gun you want so that you can get it and enjoy it sooner. You may even enjoy the gun so much you forget what you paid for it.