I"m not sure about your area, but in Michigan, I got a referral to our Michigan State University School of Veterinary Medicine- It was quoted at about $600.00 cheaper.
I am sure that you have a Veterinary school in your region as well.
Do get a second opinion though- I had two different opinions, from two different vets, in the same practice. The first vet, said it was the worst luxating patella she had seen, calling it a grade 4 and wanted the surgery done at the time of his neuter.
Second vet told me that as long as my Yorkie kept his weight down and did not complain of any pain- he may never need the knee surgery.
Lastly, I happened to take him to an out of town vet, when he fell ill a couple of weeks ago while we were on vacation-this vet commented that BOTH knees were a grade 2 and he wanted me to come back for two separate surgeries at $1,400 a pop!
So I am now taking the "wait 'n see" approach- hope this helps!