How old is your rat?
I have had several pet rats over the years.
i highly doubt that a vet would charge that much for surgery for the tumors. Though I hate to say this, it should be more a question of quality of life for your rat. if she is old enough to be developing them, it's likely she is nearing the end of her life. You can only expect 1.5-2.5 years from a rat. Any time beyond that, they are quite lucky to have had a wonderfully long life.
The problem with surgery is that very few vets know how to operate on a small rodent like a rat and dosing a sedative and anesthetic for them.. Could very well end up killing them. Not to mention stress and recovery from surgery can be quite brutal on them as well. It's heart breaking. But it may almost be better to let her live it out so long as she seems happy as still has a good quality of life.
One of my ferrets recently had to be put down. She was very old and all of her fur had fallen out.Finally she lost her ability to walk. it was so sad for me. She was still happy though, that what made it hurt the worst. She would still lick my face when I would pick her up. I knew she was better though, her not having to go through that sort of struggle.

*hugs*

i wish you and Cora the best of luck.

my rat Cora is 2 almost 3 years old so yeah i guess she is old for a rat... and yeah i kinda figures it might be to iffy with a surgery on such a small animal also Cora is a pretty small rat i am told .. when she isnt pudgy from to many treats she is small enough to close your hands around her whole body and tail with only her little head sticking out its quite funny. Cora seems to be ok other then she makes funky sounds when she sleeps now and is losing her fur. other then that her eyes are bright and she still seems pretty active...
sorry to hear about your ferret they are one of my fave creatures i almost got to have one too at one point my friends lover boy Momo but sadly without warning her dad decided she couldn't have him anymore and at the time i couldn't take him because i was moving. so she gave him to a friend that actual put him in some special home because they found out he was special or something..
i live in CA now so i dunno if i can have one however all stores carry ferret food and toys and habitats around here ...o.0... really weird...
thanks for your opinion it helps to know what others think.

It sounds like your rat has had a very long life, and that is a good thing. it means she has been well cared for. It's sad that such wonderful creatures only live such a short time.
As i understand it, skin tumors can be very itchy. If she scratches at them, you could probably get an antibiotic from the vet fairly cheap. Mine gave me one, once when one of mine had that happen as well. He also said it was okay for me to use neosporin and just apply it with a q-tip.
As far as i am aware, ferrets are not legal in california, but still a lot of people keep them despite that. At least it's good stores will still sell supplies so that they get the right food and such.
Best wishes for your ratty. Thanks for the watch too.

She scratches all the time i thought at first she might have fleas or something but we did many anti flea things as well as could never seen one on her so i eventualy gave up thinking she had some like nervous rat scratching syndrome o.0

really?! where can i find them also is that per day or week or month or something the droppers full? also would i give it to her straight or mixed with her water? ill try anything