If you have one or two snakes, shipping can be very expensive and if you don't "fill the box" your per rodent costs can be double or triple of just buying a few from your local Petco or Petsmart. Plus, you may be left with many F/T left over if they need to step up to the next size which can be a waste. I bulk order from Loxahatchee Rodents in FL, but I also have nearly a dozen snakes of varying size so I CAN fill the box and my waste is nearly zero. Plus, I only have to place an order maybe twice a year.
I would recommend prekilling. I HATE killing prey, but a snake has to eat! Then if you know any other snake owners in your area, maybe you can do a bulk order and split the costs and split the order. Just my humble opinion...