I just went to my local dentist and didn't shop around. My dentist did a visual inspection and a quick cast before giving me an estimated bill. You do get a LOT for what you pay though. Imprints of your teeth, then loads of invisalign retainers (15 on the uppers, 25 on the lowers for me, YMMV), one each two weeks. There are quite a few followups to make sure everything is fitting correctly and also to file away spaces between your teeth so that there's room for them to fit together. They also might put cement "nubs" on some teeth to give the retainers a handhold. Add all these followups and retainers and the length of time you're wearing Invisalign and the bill doesn't seem so bad anymore, especially when you start seeing the results and knowing they're pretty discrete.
The bad thing is is that it's sometimes hard to keep the retainers free of plaque, especially older ones. You're supposed to clean them with a toothbrush and toothpaste, put the brush can't always get in all the nooks and crannies of the retainer, and plaque builds up. Another downside is if you eat with them on, ugly food gunk WILL get stuck between your teeth and the invisalign, so after every meal you have to run to the bathroom or a sink to take off your invisalign and wash out the gunk.
I eat with my retainers in because two retainers into the program I noticed that the extra thickness of the retainers actually caused my mouth to bite down differently. Before, without retainers, the back molars would bit down flush together. Now with retainers, if I try to bite down with my retainers taken out, there's a space between my molars due to the fact that my mouth is so used to biting down with the added thickness of the retainers. So taking out your retainers to eat is actually very hard to do. On a side note, I no longer bite my nails. It's impossible to do with invisalign and this forced me to grow out of the habit.
