You get a chance to see automobiles that you just don't see elsewhere. The first time I went (sometime in the mid 90's), there must have been half a dozen real AC Cobras, not kit cars. My buddy and and I were walking past the acution tent and a 427 side oiler Cobra drove by us into the tent; it sounded incredible!
You might be surprised, but not all the cars go for six and seven figures. Depending on what you may be looking for, there are affodable automobiles to be had. What we see on the television coverage are the heavier hitters.
If you get chance to go, get there mid week for the first couple days. The crowds aren't nearly as bad as they are on the weekend. Also, don't pass up the chance to sit in the auction tent for awhile and witness the bidding. It's a lot of fun. And take at least one camera with lots of film or extra memory depending whether you use analog or digital. You won't regret it.