Well, according to their covereage estimate, the five gallon bucket comes out to about 28.3 liters, or a little over three 9-liter bags of ADA AquaSoil. At $57 shipped to me in California, it's almost $30 cheaper than the AS.
So I've taken the plunge and ordered me a bucket. Hopefully it'll be all that they say it is and I won't have just purchased the most expensive 5-gallon bucket in non-US Gov't procurement history.
Looks like it'll be time to redo my 10g work tank in a few weeks. Just in time for the holidays.