The cool thing is that there are a lot of vendors and games to see, demo, and play. A day pass is only $10 and a family day pass is a whopping $15. To register for games you'll have to pay a bit more, but for $10 or $15 there is a LOT of gaming you can get in. You'll get that money back just playing demos in the dealer's hall all day. If a good game demo convinces you to pick up a new game or convinces you that you shouldn't pick up that new game it will be money well spent.
Back in the non-frugal GMing days I don't know how many games I bought that got played once, maybe twice or *gasp* not at all.
If you happen to be coming to the Origins Game Fair, stop by booth 321 and say "Hi" to the fine folks from KenzerCo. While I will admit to being biased because those guys are friends of mine, it was pretty cool to sit in on a demo with the D-Team. Usually only the really small game companies have their development team leading demos. Jolly's digital battleboard is pretty sweet.
One of my recommended booths.....