The cheapest I have seen for the ten pound tub was just under 60 dollars (makes 123 gallons >cheaper than the tabs)>this will last a LONG time! (perhaps a nearby BYC member would go in "halvies" with you?)
but here is an online site for the tabs @ 23 dollars (cheapest I found) > makes 50 gallons): http://www.arcatapet.com/item.cfm?cat=15220
dont buy the sachets > these work out to around an average of 3 dollars a gallon
Randall Burkey Company has it in powder form. Just go to randallburkey.com, then poultry supplies, medications, health aids and finally, scroll down to the bottom of the page.
I have used Randall Burkey several times, and I am well pleased with them.