The conversion cylinder runs in the 250ish price range, depending on maker, model, material, size etc.. They had a nice 1858 Remington conversion setup for just for 45LC that looked somewhat like the one in my OP, it was factory setup with a loading/ejection gate for the cartridges, think is was 500ish or so.
The strange and interesting thing is, no FFL is required for the cap and ball, or the conversion cylinder. As was explained to me,(believe me I asked, and probed) at least here in Virginia
, as long as it(the cap and ball pistol frame) is not modified, modified in anyway meaning it can not be reverted back to use cap and ball at any moment, it is deemed a cap and ball/black powder hand gun, or a primitive weapon and treated as an antique, according to our state as well as the ATF. Now the purpose built, cartridge pistol designed for use with 45LC, .44-40 or any other cartridge with the loading gate, etc. that looks just like my cap and ball above, even if there is a chance you could convert it back to cap and ball, it requires a 4473.
One would be, very wise to verify his/her state laws prior to converting..