Yes, that's one of the scams in the power tool industry that they don't like to talk about. Over-priced replacement batteries and the fact, that every few years, they come out with a new design of tool that make all previous ones obsolete.
I'll keep the cordless tolls that I have, but there's no way in Hell I'm going to buy a new one, only to find out that in a few years, the battery I need for it is now no longer available.
Either that, or I'm going to start buying the el cheapo versions @ Harbor Freight, get a year or two of service, then just toss um when the batteries start going bad.