Teresa,
I experience the same thing. I think that for pet owners the photo session is more like a wedding, whereas with breeders it is more like a birthday. The pet owners may only do one or two sessions over the pet's lifetime, but breeders will bring me a different cats every season.
Jim,
I don't think people will feel much difference between a 20% and 25% discount. I like the idea of charging full price and giving away a freebie as the incentive. Maybe like a free small JPG for their Facebook profile.