First off, I do not live in the U.S.A so our laws are different. Powder I make myself and it is equivalent to Goex as have tested over a Crony. Set up cost was about $35 I use a homemade ball mill and some kitchen utensils. Powder costs about $1us a kilo to make. Percussion caps I probably bought the last box in the country at $20 a tin,,, that was eye watering.
In general I don`t use commercial percussion caps but prefer to use the toy plastic ones. They work well but I tend to tinker with them first to get consistent ignition. I remove the white insert from the cap with a pin and sprinkle a small amount of black powder into the cap till it's about half full, then give the caps a good spray with hair spray and let dry. Firearm ignition is very close to 100% I don`t actually remember a fail to fire on a toy cap that a commercial cap when then fired set the rifle off. Unfortunately even toy caps are beginning to be difficult to find here, but I have a good stock so not too worried.