Hit the facebook snake groups in your area. You'll find local prey breeders an friends to split online orders with. Near me rats run $1-6 for prey. While store are getting $12-16 for pets an $5-8 frozen.
Craigslist is another place to watch.

You could grow your own. Then you know what the prey has been fed an the conditions it's been raised in.

My BPs eat ASF, the ASF will never out grow the Balls.

Good luck!