If you have a well like me, you are probably using some sort of salt pellets.  The mortons are normally 5.46 a bag at home depot.  Now through 12/31, they are 2.97 a bag.  Pair that with the $1/2 on coupons.com, thats only $2.50 a bag.  I sometimes shop around, these bags often rip cause they are so heavy, my home depot marks the ripped bags at 50% off (of course they tape the bags up so you can get them home) this way I ended up paying $1.00 a bag which was great!