Vet training is long and costly, 5-6 years in uni in a very competitive area so you need to be the best - that can mean spending a lot on extra tutoring and literature too, as well as course material etc (if you look at the price of some of the expert bunny books around, you can imagine the price they may have to pay for all the different books they may need!). I can't remember the exact figure but I read the average amount of debt that veterinary students are in once finishing their studies and it was shockingly large!
Also vet bills don't just cover the 5-10 minutes you're in there. They have to employ a receptionist to firstly take your booking, then man the vet reception to book you in. Electricity costs money, as well as the cleaners that clean the vets daily so it's sparkly and hygienic for your visit, the rent for the building, telephone and fax bills, and all the other costs/overheads associated with owning a business property. Equipment needs to be able to be sterilised (so tends to need to be higher quality, which means pricier) or disposable (so throwing away money!), nurses available to help, e.g. restraining a dog that doesn't want its temperature taken.
Lots of medication is prescription-only, so they need a license for this, and I assume are at the mercy of whatever the supplier wants to charge, as they'll be more limited as to where they can source these from. I don't imagine there are too many choices in supplier for all their equipment too, which won't be cheap.
Vets also vary where they make their money - mine charge higher consultancy fees now but less for medication, meaning if you have pets with longterm illesses you save money (or if you practically live at the vets and they don't charge you the proper amount of consultancy fees..
:lol
Also at the end of the day, pets are luxuries, and if you aren't prepared to pay the vet bills then you shouldn't get the pet.