Interesting question- we were just having this discussion (but about dogs) last week at home! Cats are generally cheaper than dogs, though initial start up spending can be similar-
Rescue cats can be anything from free, to around £50, with pedigree breeds between £200 and £2000. Your hairless sphynx cat in the question above would set you back up to a hefty £1,000. The Ashera cat and Savana cat though have sold for 10’s of 1000’s- to me (a non-cat expert clearly!), they just look like tabby cats with long necks- evidently I’m missing something…! There’s also a pretty pricey cat called the Peterbald cat which I’m including here for no other reason other than it’s a striking resemblance to Dobby from Harry Potter (picture can be found here- https://www.pets4homes.co.uk/pet-advice/the-five-most-expensive-cat-breeds-in-the-world.html)!
After these initial start up costs (including purchase, pet insurance, inoculations, cat toys, beds that they’ll ultimately shred and other costs- i.e.- the dogs vet bills when the cat has swiped it repeatedly and cut its nose open), cats cost on average anything between £340 and just under £1000. Very helpful break down of costs can be seen here- https://www.omlet.co.uk/guide/cats/should_i_get_a_cat/how_much_do_cats_cost/.
But, even for the most expensive £1,000 ‘running cost’, it works out at costing £19 a week. Surely, for all the money you save on heating by using them as hot water bottles means they’re worth it?!