I've had pretty big bills as well, and the vets have been happy to have it paid off in regular amounts.....but I'd hazard a guess that Dragonfly is looking at a few thousand more than the few hundred it takes to spay a bitch or mend a broken leg (both of which I have paid up in my time).
After all, an op to correct hip dysplasia in a retriever costs £5000+ (a quote received).