Yeah, that's about the price I'm estimating. I forget the brand around here but it's probably Miracle Grow. It's really kind of asinine to buy several small bags of the stuff though... 8 dry quarts is just over 0.3 cubic feet, but you make do with what's available. For my 15 buckets I'd need just over 5 bags for 20% perlite. I'm lucky if they have 5 bags out on display, ha.
(granted, these aren't all 5 gallon buckets, some are 3 gallon- my season will be short so I can get away with smaller pots)