It is $58 at Drs Foster Smith and shipping is $10. I believe their shipping is based on the dollar amount spent. Playing with the numbers it is $13 for 2 buckets and $15 for 3 buckets.
Locally I've seen it at Exotic Aquatics and DNA. Both places were real expensive. Personally I just go to Plano Pets and pick up Red Sea Pro salt for under $45.