Why should something in perfect condiditon sell at a premium? A VERY long winded answer:

My first wife fell in love with the portrait painter that I hired after she had a serious accident riding a horse that we barely were able to afford. Of course, I didn't want to get divorced but she was in love with this asshole loser. My tears created pools on my desk everyday. So my course of action was to delay as much as possible. She also demanded an hour four times a week with a psychiatrist to "cure" me for my inability to resist the allure of God's greatest accomplishment - the female form. Sadly this STILL is my greatest flaw. My doctor's ministrations were a complete failure. This went on for five years but during that time she committed a number of actions that made me very unhappy. Maybe a divorce was not such a bad idea for someone that was stoned most of the time and living with someone else in front of our children which is a criminal offense in Virginia. The one great shock of my physician, Dr. Noel Schwab, that stays with me (4 x's a week X 5 years @300 an hour =$240,000) was his complete inability to understand that something that was 2% off in quality was worth 80% less than the price of an object that was perfect. We would argue about the senselessness of this for a good part of many sessions. My 50 years of experience taught me that my clients did not want any imperfections on anything they had. Noel thought that was ridiculous and that something very good was very close to having the same value of something that was perfect. The facts are simply that he was wrong in the real world. Rich collectors want flawless. Your "other" set of Cook sent as comparison is a horror missing parts of the letter press on some of the pages. No serious collector would even consider this as it is virtually unsalable. The description follows: "minor production (trimming) fault to bottom fore-corner of pages 37/8 and 303/4 in Volume I, the tip torn from bottom fore-corner pages 217/8 in Volume III, a little light foxing and occasional slight soiling; printed for W. Strahan and T. Cadell, London, 1773. Second edition. Beddie 650; Hill 783" = no market. This dealer is seeking a foolish bargain hunting novice to crucify.