I have to say only you can make the choice, but you already knew that. You're looking for other opinions, so don't feel you have to give one more weight than another, since yours is theo nly one that matters.
I personally think $1800 is criminal to spend on a pet's health since there is no guarantee it will survive, PLUS you've said it will be a burden financially.
I think people put far too much emotional investment into their pets, when they could use that time to relate to human beings. (And yes, I have had many pets.)
If you had the money to spend on this, or on a bigscreen TV or something else, there wouldn't be an issue. But you don't.
The question comes down to how much it will be a financial burden, and are you willing to suffer that burden. Five months from now when you're eating peanut butter for lunch AGAIN will you be glad you made that choice?
The question isn't about the cat's quality of life, but YOURS.
Good luck on making a decision that's right for you.
Excellent points, imho.