Aww, poor kitty, and poor Mommy's wallet
I hate when you think you're about to save some money and something like that comes up. When I quit drinking I was all excited about the money I wasn't spening on booze, and then we found ourselves with a 1k transmission bill two weeks later.
FYI, I know several diabetic cats, and they have all gone on to live purr-ductive happy lives.