Everything EVERYTHING should be written on the sales contract:
Price of car
doc fee (which used to be called ADMU - additional dealer mark up)
There should be NO estimate of anything. If they don't know what the fee is, they are lying or stupid.
Doc fee is whatever the dealer wants to charge. In Mass, the fee is usually written in specifically on the sales contract and the sales guys cannot change it. But guess what? When you're making your deal, ask them what it is. They will tell you. Then use that in your negotiations. Some states (Rhode Island, for example) limit the doc fee by law. There, it cannot exceed $5. Some dealers include something for that fee making it less bogus. Maybe inspection sticker, maybe the runner's fee, maybe a full tank of gas, maybe coupons for the first service. This is not set in stone by anyone. You need to be aware and negotiate around it.