Please don't comment on the amount of money one spends or doesn't spend on their pets. It is their business and nobody else's.
If person X wants to spend thousands of dollars on surgery for their cat it is their prerogative and should elicit no comments on how they "must have more money than brains".
Similarly if person Y cannot afford to spend a fortune on their pets then there should be no commenting on "how cruel and heartless they must be not to bankrupt themselves to save Fido".
I personally have a limited amount of money I am able / willing to spend on my cats. I am not a bad pet owner because of this.
And while I hate it when people get pets on a whim and discard them like yesterday's trash...please respect that the decision to get rid of a pet is not always one of callous disregard. Maybe someone has developed an allergy, lost their job, maybe the pet has acquired an intolerable habit ( peeing on furniture is one I have personally encountered ) or become aggressive.