where do you get your salt from

[vr697getta]

i was about to order from doctor fosters but after shipping its 62 dollars reef crystals is the salt 160 gallon bucket.i priced it out if i buy the 50 gallon bag for 20 bucks i am only saving 2 dollars for every 160 gallons. is there a better place or should i wait for it to go on sale and buy bags for now.