I have heard many of these stories and avoided many of them myself. It is amazing in this day and age that we still "haggle" over cars. It is like buying something in a third-world market.
Locking the customers in the office - WTF , until they give in and purchase a car, isn't there a name for that, like holding people hostage, or against their will, or false imprisonment , or all of them ?
I had a dealer took my "trade" on a test drive then when we couldn't agree on price, they couldn't find the key or the car. I walked out and found the car in the back lot and had them get my keys. I called my wife to get the 2nd key and bring it and told them they would get a visit from the police for stealing my keys. I stayed by the car and one of the porters brought the key over, not the salesman or the sales manager who was "giving me the best deal possible". Those guys were crooks.