Hi, most all shipments of BP, subs, smokeless, primers, and caps require a hazmat fee. That includes Black Mz The hasmat fee encourages buying larger supplies of shooting propellants and caps.
Olde Eynsford costs $19.99, Black Mz $26.99 from Graf and Sons:
https://www.grafs.com/retail/catalog/category/categoryId/3500Assuming a 20gr charge for the 1851, the added cost per shot using Black Mz over Olde Eynsford is $0.02. IMO considering the advantages, even at a $27 price for Black Mz, Black Mz won't break anyone's bank.
BTW, caps cost ~$0.04, and if you buy your balls, swaged 0.380" ~$0.13, Black Mz ($26.99) ~$0.08 per shot. total ~$0.25.
Regards,
Richard