Uhh, say, 20k? My sister died and I've been taking care of her 18-year-old cat with health issues. It's my only living link to my sister - and aside from a couple cousins I don't see much, she was my last living relative. I'm not ready for another loss right now, and it also kinda feels like letting go of the cat is also kinda letting go of my sister, so I'm trying to keep the cat as healthy and happy as she can be for as long as possible - it's just really expensive (extra special diet, multiple medications, periodic tests). But today the cat raced me down the stairs, then yelled at me for making it cold and wet outside, then complained that her food was late, then snuggled up next to me at the computer. It's all worth it.
Edit: I'm estimating it's been at least 10k so far, just for emergency treatments, getting her stabilized, then diagnosed, and then coming up with a set of food and medications that work. And then I'm estimating another 10k to care for the cat in the future. She's a good cat, even if she yells at me for letting her see the bottom of her food bowl ...