The internet changed everything. Buyers and sellers can find each on-line 24 hours a day. The migration to the internet has had a very significant impact on prices of old instruments and books. The prices for common items such as books by Breed and modern instruments have tumbled. These things are always available on-line, so collectors find no reason to pay a significant sum for them.
Buyers control the market here, since sellers are plentiful.
Rare instruments and books have increased in price. A seller with an uncommon item will find many interested buyers. Bidding wars occur when this happens. As you will see, most of the MarketWatch database comes from transactions occurring on Ebay, which is an internet auction service. Ebay is way ahead of the other internet auctions services.