He is doing this as a guide folks, not set hard and fast rules to pricing for every drum. Many other industries (Guitars, cars, furniture, ***elry etc.) have price guides and they are just that, GUIDES. Here is the reality check, I, like many people on this board, resell drums either in shops, at shows or on Ebay or Craigslist and for me I know that having a median price line to work from is a helpful thing. If I have a snare that I picked up at a yard sale and it ends up being in really good condition and I look in the guide to see that the are selling between $300.00 and $650.00 depending on condition then I know that $500.00 is going to be a more realistic price if I want to move it quickly. Don't get me wrong, I know that I may be able to get more and could possibly get the higher dollar amount if I list it in an auction but I could come up short there as well. The drum is only worth whart someone is willing to sell it for and someone is willing to pay for it on any given day. If the drum can fetch prices as high as $650.00 then you can list it for that but then you may end up sitting on it for a while and while I am in this for the love of the drums, the drum doesn't make me any money sitting on a shelf, it only makes me money if it sells.
In the car world, 20 years old is considered classic (vintage) and anything over 40 years old is considered antique. I have always used this as a guidline when looking at old drums. You may want to consider somethiing similar George. Again, not set rules but just a guideline. Write your blue book, it is a free country and those who don't want to use it don't have to read it.