In this case about $300.  My cat Bauldy, aka Butthead, had to go to the vet.  His front right leg was all swollen.  About twice normal size.  His left foot is already gimped, probably from the dogs.  He is almost 19 years old.  I could have left him and let nature take its course.  But if he was in pain or something I'd feel bad.  Of course the vet suggested a xray so he could really tell what was going on.  More money...  Results in, and he has some kind of cat degenerative heart disease.  Something myopia.  Basically his heart was 3 times the size it should be, and it was filled with fluid, as were his lungs and arm.  Now that I decided to go this far I mise well treat him, he is going to die, regardless though.  So now a blood test to tell what kind of medicine and how much.  Oi, damned conscience.  I could have euthanized him I suppose, but I've had him for 19 years.  How do you do that.  On top of all that this morning my female dog is favoring her right leg, the one she had a torn knee on... great.