The most common causes of regurg is not enough heat, handling too soon after a meal or parasites.
If you are not handling him after he eats, then you need to look at the other two. Your temps on the hot side could use to be brought up a tad. IT also never hurts to have a new animal checked out and wormed. (Everything that comes into the house, goes into quarentine, gets wormed and the cage treated with provent-a-mite.)
If he is eating f/t fine then don't switch him back to live. Just wait 7-10 days and try refeeding him. This time use a mouse from a different batch of frozen rodents.
** For those of you wondering about retail prices, let me explain the wonderful world of retail. Stores pay wholesale prices for everything, in our example ball pythons. They pay about 20-30 bucks each for the baby balls you see in the store. Since the whole idea of our economy is to make a profit, they need to charge 90 bucks, to cover the cost of the animal, the cost of feeding the animal, heating the animal, rent for the building, electric, water, gas, employees pay...etc.
So you see that, yes they are WC and more expensive than a private breeder. Chances are most private breeders just want to help pay the feeder bill when they sell an animal. They are not worrying about rent, utilities, etc. For example, I sell my baby leopard geckos for 20 bucks each. This doesn't even come close to paying for the upkeep of the babies much less the adults. But I figure that if I can buy a box of crix, in addition to the fun I had breeding the adults, watching over the eggs, and nurturing the little guys until they go to new homes, then hey the box of crix is an added bonus. The same leopard geckos in the stores would cost you 40-80 bucks.