Interesting. It is closer in concept to my "simples". Cheap magic of limited duration. Personally I would cut the cost even further. As 12,000 gp is well out of the range of the kind of person that would be the target audience of such an item, the common villager or farmer who isn't going to see that kind of money in their life.
It is a balancing act to keep some magic rare and expensive while other kinds are common and cheap.