Right, that's exactly the point. There was almost 0 money in the pure sale. All of the money is in high interest loans (via kickback from the financing), waterproofing treatments, "extra" insurance, service plans managed in house. The profit on a car night be negligible, but a cheap car sold with gap insuranxe is likely a days salary!
The car business is a giant recursive function where cost can be added at every step.
The sales price may have been low but the dealer has lots of ways to add pure profit:
* sub-prime loans with high interest
* gap insurance
* alarm systems
* extended warranties
* window tints, undercoats, towing hitches, etc.
The buyer might also have a trade in which conveniently starts the whole process over again.
The "Forbes list of Billionaires" has several car dealers in it.