If it's a true professional fit, that's a really good deal. Most professional fits are pretty extensive and can take up to three hours.

I would check to see what kind of fit it is. If it just involves someone watching you while tweaking your fore-aft, saddle height, and stems it may not be worth it. That's something you can do on your own.

You should also ask around or look for reviews on particular fitters. You will want to get someone experienced that knows what they're doing. I haven't been trained, but give me an hour and I can tweak a person's position on the bike. The position would work, but probably not be the best since I don't have that much experience with fitting.