Well, most of the TSR catalog is available for sale as a .pdf now, so the issue isn't really whether or not you can find a hard copy so you pirate. The issue originally was, wizards didn't even offer the .pdfs for sale, so you had no other choice.
Sadly things get rarer and rarer, and so the value goes up. The prices are that high because someone is wiling the pay them sadly.
You can always buy the .pdf and have your local printer print and bind them for you. I've done that with Greyharps OD&D compiled, and Caverns of Thracia. Far cheaper.