Acquisition and daily maintenance isn't bad, it's the unexpected vet visits that add up. For 5 cats (1 barn, 4 indoor), we spend about $40 in litter and $60 in food/month. I think the most expensive was $75, adopted from a rescue. The barn cat came with our house, two were strays, and one was free through a rescue that desperately needed to clear space. One who died several years back was from a rescue and he was $100, I think. The strays still cost an initial vet visit, though fortunately both were fixed already. The annual vet checkup with fecal exam and shots runs about $100. Dental cleanings under anesthesia run ~$250-$350, but they don't necessarily need that every year. We have one who has naturally perfect teeth that stay clean, and one who's had to have a ton of teeth removed. We budget a lot of sinking fund money for vet bills, between all the cats and the dog. Unless you really feel strongly about getting a cat, I wouldn't. I love mine and wouldn't give them up unless we were at risk of starvation, but I wouldn't recommend acquiring this many.
These are the big vet bills I remember from the last 6 years:
1) Sudden blindness and circling, ICU stay, diagnostics, check ups, cancer diagnosis, hospice meds, euthanasia = $1800
2) Broken leg, Xrays, cast, numerous rechecks, have to board cat at vet when gone for the weekend, more xrays = $2500
3) Swallowed half a spool of thread while we were gone all day, emergency surgery = $2200
4) Major dental with half the teeth removed = $1500
5) Nasty chronic cystitis, lab tests, meds, put on antidepressants! = $780
6) Mysterious hair loss and dermatitis , visits, tests, rechecks, meds = $550
Did you know you can foster animals for rescues and shelters? You take care of them short or long-term, the rescue pays the bills. The only hazard of that is that is can be very hard to give them up.