I found a cheap way was to buy a huge bag of epsom salts that was intended for commercial flotation tanks (the type spas would use for new-age spa treatments where customers quietly float in a sensory deprived flotation tank). Searched around on the internet and was able to have a bulk bag delivered to my home.
Worked out great. Saved lots of money. Bought a big bag and just use it for my baths occasionally. I don't keep the big bag in the bathroom but a place in the house with dry air. It doesn't keep as long in humid rooms. Sometimes in the bath I mix it with plain bath salt (no perfumey stuff) to help with joints. I also hear it's nice to mix with oil, baby oil, etc. if sky dry.
It's good to brush your (dead skin off) skin all over your body beforehand (in the direction of your heart to stimulate circulation), stay in only 20, on the outside possibly 40 minutes, not too hot (aggravating nerves), then shower any residue off. I like putting on my podcasts / spiritual music in my ear phones and going into a healing zen state and talk nicely with my healing body.
I found it hard to find pure, unadulterated epsom salts and also plain bath salts. Everyone wants to mix in some special blend of cosmetic stuff and then charge a fortune for a small packet which adds up if you are using it regularly.
Natalie