You can find some games being sold for like, $10-$20 if you go to a swap meet or a flea market. More rarely, you can probably find one sitting in the shelfs in a Goodwill or any similar secondhand store.
Anticipation is pretty great if you have friends. If you're looking for a kind of "out-there" single player experience, A Boy And His Blob is a fun game to get lost in. You can find both for easily under $10 on sites like eBay.