Okay, I totally did not mean to freak you out...let me start again:
Yes, you pay AADSAS a fee to process your application, in addition to the charge of each school they send your information to. You cannot avoid the system unless you are applying to a school which does not use AADSAS.
Each school, once they have received your AADSAS application will then send letters requesting secondary materials, including an application fee. These fees can range from $30-75 typically. It is for this reason that it is very important that you are selective about the schools that you apply to. Do not waste your money, but also do not be so cheap that you bulldoze your chances.
Interview fees are things such as hotels (look into hotels.com), airlines (airtran, cheaptickets.com), interview attire, and hopefully eating, etc.
DAT fee is the price of the test, in addition to sending the scores out
and finally, deposits -- once you get accepted into a school. These can range significantly. I know for the school that I am attending, the deposit is only $30.00, but they can go all the way up to as much as $2500.
In all honesty, all of these fees are worth it in the long run. If you become a dentist, you will pay this off one day. The rewards more than outweigh the costs. I think many other SDNers will agree with me here.
I spent around $2500 on the whole process to go to a school that if I'd have know I would get in, could only have cost about $250 bucks. The things is, you just never know...Don't worry about the price during the application process, it'll pay you back later
Best wishes!
Beach