Personally, I don't think there's a such thing in spending too much money on your pet- this money stuff gets quite messy if you can't afford it. You hear so many stories of people spending $10,000+ because they really care about their pet. When you adopt a pet, you need to be prepared for the costs- almost like paying for a child except no expensive school fees. However, hospital fees and vet visits replace those fees. Just like everyone above said so, if you're not willing to pay for your pet, then just re-home them (when I say 'you', I'm not directing it to 'you' but in general). I know families who don't bother taking their pets to the vet or even desex them.
My cat recently had surgery for teeth extraction and boyyyy was it expensive. It was already ~$200 for anaesthesia, another $80 for X-rays if we wanted to and then $100
per tooth- the vet suggested that 10 of her teeth had to be taken out but we told them to take out the really bad ones because 10 may be too overwhelming. They took out 8- that's already $800. Was it expensive? Of course, especially how my parents just bought my sister a car right at the beginning of the year. But it's one of the things you do to sacrifice for a pet.
And since secretly_a_poet shared a picture of their cat,
I wanna show off my cat too! (this is Meg post-surgery)