I'm not 100% sure about the fabrics, dyes, glues and any other treatments craft store plants are made from.
As a general rule, if I'm in doubt, I don't put it in the tank.
It may be cheaper, but it's also a gamble. What if a chemical taints your water and all your fish die? Then you have to restock, as well as buy the more expensive plants from the LFS, so it's not saving you money in the long run.
Also your fish are living creatures, I'm sure they wouldn't appreciate being exposed to any chemicals that might be in a fabric plant not intended for use in an aquarium.