My vet doesn't charge an office fee and also doesn't charge for a checkup if they get shots and de-worming. So no discounts there. My mom's vet does give a discount when you bring an entire litter; he only charges one office fee.
When I brought in a litter of kittens (5), my vet discounted me and only charged me for the price of the checkup for three kittens, this brought the cost down a lot.
I really think it depends on the vet though, if you can convince the office manager to give you a discount or not. Call a bunch of local vets and find the best discounted price.