The pet stores are pricey and many people do not realize that they are available at many bait shops for a much cheaper price. Now if you want them as pets many times the bait may not hold up as longer since they are not treated as well, but due to the price difference you can pull the dead ones out and I still think you would come out ahead.
A few times back at the bait shop I was getting me some FHM to go fishing and there were a few people there looking for Rosies and they were out. They used them to feed their fish at home. I told them to just get some of the blacks as they are the same fish just different color and that their fish would probably not care that they were not pink, at least if they were hungry.
Told them they could get much more food for there fish rather than buy the rosies at any big box store or pet shop.