For me it always depends on the quality of life that the animal will have after the treatment.
If it only prolonging the inevitable, then, No. No matter how much I care for the animal, I wont just prolong an 'existence'
However, for a young healthy animal, that will retain its quality of life, yes, I will fund the treatment, and have done in the past.
Also, it depends on whether the animal is put through a lot of pain, as whether I believe treatment is a for the animals benefit...or our own.
Matty