Seems to be a fact of wargaming life nowadays. But there's not much you can buy for less than a tenner nowadays. Even 'Sword and Spear' that is self published is £14, but you can often get 25% off, or download a PDF version for £6.
They seem to justify the price because of the detailed army lists, and there's clearly still a massive interest in DBA - I got enquiries from as far away as Manchester when I put that mini-tournament on in August.
I'm getting a copy, and I'll let you know if it's much different from the rules they published recently. As I say, I think the army lists are what we are expected to pay for.