Make them actually live within the bounds of their beliefs. No plastics, no medicines except local herbs, keep the cow in the house for heat, no fresh food in wjnter, walk, outhouse.
Im reality there was a lot of trading through history, herbs were used for medicine, and not just locally. Flint was imported to areas where it could not be found. The list goes on.... at some point we have gotten too far away from some of this