Keep in mind that in 76 if you bought that powder you bought it across the counter, there was no mail order like today. You also paid cash or check, unless you made enough to have a Diners Club or American Express and you paid the balance off on those every month. Chances of a gunshop taking those cards was pretty dang slim..
If you bought a house or car you put 10-20% cash down to get financing, if you bought a new rilfe, pistol etc, you paid cash or put it on layaway, and you did not get it until it was paid for,, no loading up the Visa back then.. Yup things look like they were cheap, but looks can be deceiving.