Where I used to live my local pet shop always had plenty of kittens and puppies for sale...mainly Jack Russel, Yorkshire, Highland terriers and other smaller breeds, kitten-wise they used to have British Short-haired, Siamese and Persians. MInd you, these would be sold at breeder prices, the Jack Russels cost around 1200 pounds and the kittens would fetch for 700-1000 pounds each. I have a British Shorthair myself, felt especially bad for those in the shop.
Only when they had difficulty selling them would they lower their prices to 400-600 pounds, but that wouldn't be written next to their enclosure, people would have to haggle with the shop owner. You could regularly hear these conversations on the phone and in the shop too, front of the other customers. In their defense, the animals in the shop were always in tip-top condition and they were well cared for, everything from the feeder insects through the rodents to the kittens and puppies. Though it didn't make it any less of a business with the main goal of making money.
My boyfriend's sister bought a 'teacup' chihuahua from a pet shop, with no papers, no nothing for 1500 pounds. Now, grown up, this teacup chihuahua is a size of a rather large regular one.
Also he was taken at one point from her, due to a fear that he may have rabies, as he was smuggled in from Slovakia from a puppy mill.
I think pet shops just need to stop selling animals, full stop.
You might feel bad for this cat, but at the end of the day, by buying it, you're only supporting the trade of the pet shop and at worst you are supporting a kitten mill. It will be replaced by another kitten as soon as you buy it.