Well, this was an interesting rabbit hole.
I've had 2 cats pretty much the entire time. There's been some variation in which cats of course, but I had Sibley from 2007 (really earlier, but I wasn't paying her expenses) through 2019 when she died, and Arwen from April 2008 through Oct 2022. Since Sibley died I've had a variety of different cats, most of which had higher medical bills. I now have 2 kittens, so I'm in the high cost early period and it will go down from here (SO MUCH FOOD).
This includes: food, cat adoption fees, toys, litter, supplies, vet costs, meds, and pet sitting. Basically, if I bought it for the cats, it's in this total. From 2007 through 2013 I worked a job that I traveled a lot and thus I paid a pet sitter to take care of the cats while I was gone, this was a lot.
Total 8/1/2007 through 12/16/22 (the entire length of tracking I have): $44,782.24. Forgive typos if the annual doesn't actually add up.
2007: 384.11 <-- started in August
2008: 1,413.72
2009: 4,228.29 <---lot of vet bills, there was a neighbor cat beating up my cats repeatedly until I figured out where the cat lived and talked to the owner, who thankfully did something, then I moved
2010: 2,947.71 <-- pretty sure that was the year Sibley got about a dozen bites from a raccoon/possum
2011: 2,335.24
2012: 1,873.60
2013: 3,275.35 <-- extra costs cause I moved cross country, so extra vet bills, supplies, etc
2014: 2,160.14
2015: 1,667.47
2016: 1,935.55
2017: 2,159.17
2018: 3,888.74 <-- vet costs for Sibley, she was nearing end of life
2019: 3,123.33 <-- lots of vet costs for Sibley, then she died, then extra food for a sick foster cat (no vet bills, but I provided food/litter), then adopted Jill
2020: 4,872.48 <-- Jill died unexpectedly so extra vet bills, Arwen was sick but recovered, got Rosie and she had some health issues
2021: 1,717.11 <-- had to return Rosie, then only had one cat for a good chunk of the year, plus parents probably bought some stuff since they were living with me.
2022: 6,799.59 <-- adopted Elrond (hyperthyroidism so daily meds and periodic blood tests), Arwen got put on anxiety meds, Elrond got really sick and died, Arwen got sick, then got better, then stopped eating and died, adopted 2 kittens Beren and Luthien, so their adoption fees and baby shots. $4100 of this is just vet bills and meds. And I bought probably $200 in toys since a lot of my stock was old or unsuitable for kittens.
I'm not done for the year either, Beren goes in next week for a recheck as she's currently sick (kitty cold, she's doing fine) and will need a microchip, plus no guarantees I won't need more kitten food as they are both eating a ton of food. 2023 the kittens will need more shots, and are still growing so the food bill is sky high. But after that, the total costs should be much lower for a long time.
Edit: I said 2-4k on the poll, but clearly it varies significantly. 2022 just happens to have been an insanely expensive cat year.