I haven't tried the Graff BP but did buy some Elephant brand from them many years ago for about $6 a can. I will say they are super nice people to deal with. They will jump through hoops to make you happy.
Have a look at this place for powder. The price includes the shipping and hazmat. I always make the 25 pound buy and then sell a few cans to my BP buddies because 25lbs is more than I need for a long time.
The last time I bought from them the powder cost me a little under $10 a pound. I still have several pounds left.
If you do buy the Grafs powder report back how you like it. I bet its good stuff.