If, you're just starting, or just considering building some guns, I'm not sure that buying really high quality files is worth the cost.
I bought some Nicholson files at Home Depot, that also have the name 'Black Diamond', or something like that on them for only 5 or 6 bucks for the small ones, and 10 or 12 bucks for the larger ones, and they seem to cut as well as my more expensive ones. Now, I don't know how long there going to last, but I'm sure you could get at least a few rifles out of them before they give up the ghost. Use the money you save on files to buy gun parts for now, and if you decide to build guns a plenty down the road, then put out the $$$ for the big bucks ones, and use the less expensive files to make into scrappers and such.
Tight wad John