Since they no longer exist in the wild, ALL gp are pet shop gp that have been bred anymore. Whether they end up in private hands for generations or not, doesn't matter. If all pet shops stopped selling them, and people stopped breeding them or allowing them to mate, they'd be extinct in 10-12 years assuming one lived abnormally long.
Here, they are $35 locally and for whatever reason, the hairless ones are double that. Unless you have a few hundred of them giving birth constantly, I don't see how anyone can make any money "breeding" them, especially considering food + hay + veggies can easily top $60 a month for 2 gp. Selective dog breeds however could bring in a ton of money as people pay outrageous sums for some dogs. But even with dogs, same applies. If they are no longer allowed to mate, all domestic breeds would be extinct in 20 years, save for the couple that live abnormally long.
Like it or not, people are now responsible for gp's survival and the people "selling" them are the reason they still exist. I personally have mixed feelings on that, more so for the fact they don't exist in the wild, but unless we can reintroduce them to a place they are not sitting ducks for feral house cats, it's just the way it is anymore.
P.S. not condoning or advocating anything here, especially anything that violates forum rules. Just saying it's the way it is.