We have 6 atm (the atm doesn't imply i'm waiting for one to pop its clogs btw, it's because one of them is a rescue who is technically supposed to be rehomed soon, although that's unlikely now)
I buy Oko Cat's Best litter as it's miles better than any others and therefore makes my life a little less revolting... that's 7euros a bag, one bag lasts 1.5 weeks roughly
I feed 2 tins a day of whiskas, kite kat or similar which is about 9 euros a week, although i'm switching back to Bozita as i think it actually works out as cheaper and is far better quality.
I feed high quality dry twice a day too, Iams at the moment but i switch constantly as the little feckers stop eating it if i feed the same brand for too long. That's over a tenner a week i'd say, hard to judge though.
Worm tablets are 20 euros every 3 months, spaying/neutering 70 euros once off, random vet trips can be any amount. Although if you feed them good quality food and take good care of them vet trips are usually minimal, the only one of mine i've had to bring down to the vet was the little lad i found at the side of the road half starved and with infected eyes.
btw... dry food only diets can lead to kidney failure and really aren't wise. Cats just simply don't instinctively drink enough water, they're desert animals designed to get most of their moisure from food.