No doubt about it, finding real black powder these days can be difficult for most of us.
There is one little gun shop a couple states over, near my childhood home, that sells Goex for about $19 a (1 lb) can. Ended up being about $21 per can after tax.
Other than that, the last Bass Pro shop I was at wanted $25 per can, ended up being about $29 after tax.
Needless to say, I stock up at the little gun shop whenever I can. Bass Pro must make alot on Goex... I would order Goex in bulk online from Powder Inc., but I really wouldn't feel comfortable with 25 lbs of black powder sitting in my studio apartment! I don't think I'd make it out if there was a fire or something!