Took my grandson out doing informal trap shooting using a double barrel flintlock 12ga. shotgun. Used two flints (black English) and shot over 100 rounds with out any problems. In fact the flints are still in the gun and shower the pans every time. I do believe quite few years ago I paid under $5.00 for 6 of them and still have at least 3 left. I do place the flints in leather, however.
Again quite a few years ago when I was shooting in SASS in the Frontier Class, I used two Remington 58 Army's using real black powder, that I purchased from the Powder Horn umpteen years ago. In fact I ordered 50#'s of mixed FF,FFF, and 2#'s of FFFF, I still have about 7#'s of mixed powder left, including a # of FFFF.
As far as caps go I bought 5000 tins of Remington and CCI #10 and Number #11, and still have quite few of both caps left. I've always made my own wads using felt and a cork type material using a punch I believe I got at TOW, and using Thompsons Bore Butter for lube. As far as cost goes, now days I don't have a clue as I poured my own balls from pure lead that I got for free, from a plumber friend. At the time it was below $.05 a round.