I would check it out if not too inconvenient. Twenty bucks per pound is a good price for any kind of black powder these days. On top of that, any order that requires shipping will cost you an additional $40 or so in shipping and HazMat fees, whether you order one pound or ten. If you can buy it locally, especially at $20 per pound, you’ll save a lot of money.
I think some places buy powder in bulk and have it packaged in containers with their own label (e.g. Travelers brand, or Graf’s) to sell a little cheaper than the name brands. Also, some of the “reenactor” powders sell for less than the better grades. As far as I know, reenactor powders are intended for blank loads. I hear they work safely for propelling ball or shot, but they may not burn as cleanly or consistently as better grades. I have a pound or two of Goex Reenactor powder but I have not tried shooting any of it yet, for blanks or ball.
However, I’m getting ahead of myself here. I think if I saw a sign for black powder at $20 a pound, I would want to check it out. Who knows… they might have percussion caps, too…
Notchy Bob