I read that they used to be viewed as a cheap cut but that has changed a bit.
That's exactly it. In early 2000s I used to buy pork cheeks in the mainstream supermarkets, and they were a lot cheaper than the equivalent weight of mince/stewing beef etc. But IIRC Jamie Oliver did a recipe using them, then they became popular and obviously tripled in price.
A little bit like tongue, they have a coarser texture and we used to slow cook them rather than quick fry.
Oh but to keep on topic, I've never seen beef cheeks in a restaurant or for sale in a shop