Thanks to all these wonderful replies, it looks like I will be going over budget. As far as the main purchases, it looks like barsoomcore hit the nail on the head:
barsoomcore said:
Wheel of Time -- give it a look, but it's not really the sort of thing that can just a "part" of a campaign world, which is what it sounds like you're looking for.
I think your two best bets, by far, are Oriental Adventures and Nyambe. Both present very different cultures that still fit within the ground rules of standard D&D so that your characters could, in effect, walk to these places and not find that the rules of physics (or rather magic) have changed all that much. They could learn some cool stuff, maybe take a prestige class or learn some new spells or weapons or whatever, and go home if they liked.
Both books are spectacular, well-written and illustrated, full of ideas and inspiration and thoughtful rules to make adventuring in their settings a completely unique experience.
This is exactly what I want, and for these reasons, as well as the free Lorebook, Nyambe has replaced WoT at the top of my list. Sounds like both Nyambe and OA will be good reads, and are likely to have a few things I can draw into my campaign. If I like them as a whole, here comes a new continent or far away land to drop in.
On top of interpreting my goals perfectly, I respect barsoomcore's opinion because I dig his campaign setting. Your site is great, and I would love to play in a Barsoom campaign some time. I frequently look at your site for ideas.
Samothdm, have no fear. I must admit I felt like a downloader of pirated MP3s, claiming "If I really like it I will buy the whole album, so the artist is actually making a sale out of my getting a free sample." But this turned out to actually be the case. If the campaign book were only the Lorebook with decent artwork and a hardcover, I would still buy it.
So after getting those two, I still don't think I will be able to pass up The Hunt: Rise of Evil. The concept sounds great, and I will probably have to get it.
It is also well past time to wet my feet in the Scarred Lands. Most likely I will browse through a few offerings and see what strikes my fancy. I am sure that the city books are well done, but I think I will be more likely to go for Secrets and Societies or Relics and Rituals. Either one should give me some immediately useful info, and a taste of SL.
Wallet, brace yourself.