Paizo apparently has all of the rights to all of the old TSR publications. They're now offering a wealth of old D&D and AD&D modules and rulebooks to download in pdf format.
Note to Paizo: This is a very cool step, except that a lot of the materials are obsolete, and only of interest to many of us as nostalgia tickets. Being a full-time software guy, father, author, podcaster, musician, Berzerk player, NHL fan, movie-watcher, and hermit, I just don't play any RPGs any more. So I'm not willing to pay $4 a pop to download scans of the old D&D books.
If you're making a nice profit from this PDF catalog, then I can't make much of a case for you to lower the prices. But - if there isn't much consumer interest - then try a rate-slashing. How about $1 per pdf? Why not even offer a few of the books for free?
I browsed through the titles on those pages, revelled in nostalgia at all of the artwork on those old book covers, but that's where it ends for me.
Incidentally, I think the original module used some kind of invisible ink, but I'd still love to see an electronic version of "Maze of the Riddling Minotaur".