re: Most money you've negotiated off a new vehicle

Depends on local/area (within 60 miles, usually) competition of that same dealer. Depends on how much the vehicle sells for. Depends on factory incentives. Depends on how long it's been sitting on the lot, and how likely they are to selling it soon. Depends on invoice price. There are easy 411's if you google about the "buying a new car process." Also depends on your patience to have to buy one. If you can let them cook for a solid month while they keep trying to sweeten it, you will catch them trying to meet monthly quotas.

The internet was a "new" car salesman's worst enemy. Now used cars, they can sit on the lot and rot until they get what they want for it.