Whew - $475 for a ML barrel on my Encore is more than I'm looking to pay. But it's very tempting. I hadn't thought about custom options - time for more research!
If you consider the cost of shooting smokeless powder in a muzzleloader is at least 50% less than 777 or anything else, the savings add up fast if you do any shooting.
I own a Savage muzzleloader and I shoot smokeless powder thru it and it is heads and shoulders better than any other alternative. No smoke, no mess, no rust, less cost, more accurate, faster velocities, etc.