In the first case comparing pro$$ies to burgers and car mats:
Food and car purchases are legally binding contracts with companies that have a public image they would prefer not to be tarnished. Secondly, you have to consider the cost of the omission. A £30 car mat is a tiny fraction of a £10,000 car which the dealer would have no problem putting right.
Dealing with pro$$ies is all about discretion, disposable income and gambling (punting).
There are no tangible gains from visiting pro$$ies, you take £xxx give it to some strange woman and she will put a smile on your face or not. You live and learn, report your findings relating to bad experiences on a forum so that the next punter doesn't suffer a similar disappointment. At the same time you take heed of other punter's warnings and avoid the scammers, liars and cheats.
Causing a scene, indulging in criminal acts of revenge or threats of violence will most likely cost you more than what you are ever going to recover, which is what the cheats already know and how they get away with it. If you have a solution to recovering money from a scamming pro$$ie then your next trick should be how to get blood from a stone.