I just bought After the Battle's
'Blitzkrieg then and now' for £6.50 in a charity shop I don't usually bother with.
Hehehe,
Made my week it has.
On books 2nd hand and new at a reasonable price; seek and you will find. Just takes time and perseverance/obsession.
Of course every now and then you've just got to splash out on that pricey tome. In my experience every seemingly expensive high quality book on a subject I'm interested in has proved to be an absolute bargain in the long run.
Cheers,
Adam.