Having worked in a clinic, and being a pet owner I can see both sides of things:

Most of the time, most vets are able to justify their charges. There are a few cowboy vets out there who charge a lot just for the sake of it, but luckily I don't know any and I haven't heard any outrageous stories about it, but I know that it does happen.
You have to remember that unlike a regular human doctor, vets are all specialties rolled into one - they are GP's, Surgeons, Obestricians, Gynacologists, Neurologists, Pathologists, Paediatricians, Chemists, Radiologists, Opticians, Dermatologists, 'Coroners' (for lack of better word), psychologists among a whole ton of other stuff, including being business people. To get to be all of this out of 5 years of study is really really intense, and most of the time comes at a personal cost.
Vet bills are usually so high because Veterinary Medicine is such a specialised field - all the equipment vets use is very expensive, very specialised, and usually few and far between.
Hence the cost of having this equipment is passed on to the client, otherwise the business wouldn't be able to function, and your favourite vet or clinic would close down.
The reason why vets are (or should be) constantly getting newer, better or more equipment is so that diagnosing an illness or disease takes less time, is less invasive (radiography - xrays and ultrasound - as opposed to surgery), therefore less stressful to both the patient and owner, and ultimately, less expensive. I would rather pay for 3 or 4 xrays to find out my cat had gas than to have it go through surgery to determine the same thing.

Also the vets I worked for were always on the lookout at places like Amazon.com for new textbooks to aid in their continual learning. We rely on vets so much to have the answers to our questions, so it makes sense that they would want to read up on the latest and greatest techniques or equipment. A well equipped clinic with vets who are constantly looking to further their knowledge is the best thing my pets could ask for - and I don't mind paying a bit extra for the peace of mind of knowing that my Vet is doing all they can to help my pet.

By the way, vet nurses or technicians don't get paid a whole lot of money (certainly no where near as much as vets do!), so I'm not just saying this because I am a vet nurse and my clinic charges a lot because they need to pay their staff well, staff wages are probably the last thing on the vets budget priority list!