Also consider that historically serial numbers are a fairly recent addition to drums (I don't know that they were present consistently before the 50's-'60's for all manufacturers???). Therefore, the inclusion of them to the instrument was probably more of a benefit to the customer for reporting a theft loss, rather than serving some internal function that aided in the accuracy of the inventory process. In other words, Ludwig didn't set out to build a complete Downbeat or Hollywood (or whatever set) but rather they banged out a bunch of shells, placed them on a shelf, and then filled orders/created kits.
For comparison, I had a set of 8 melodic/concert toms that I bought in the 70's and the numbers were not that close: 6" = 1506034 / 8" = 1506027 / 10" = 1506153 / 12" 1501391 / 13" 1506185 / 14" = 1505998 / 15" = 1505592 / 16" = 1507415. Ideally you would think that a set like this would be sequential, but the drums, although delivered at the same time were quite likely manufactured a different times - and again this may mean just the finishing step or even batched in shell lots?? With any manufacturer at that time, who really knows?
Todays process are a bit tighter and some manufactures will actually build a kit and keep it together through the entire process and some still batch. Makes it a lot easier to keep serial numbers sequential when you're just placing stickers on the inside of the drums these days (plus, back then nobody really cared about this stuff - old drums were for people that couldn't afford new drums!!!)
I would echo what Hobbs said, that it is the nature of the kit/components that will drive the true value before the sequential nature of the badges (although for certain buyers that is important enough to justify some additional value).