RE: how come...?
The muzzle loaders you'll find at Wal-Mart, Academy, etc are not bad guns. They sell them cheaply because they buy so many of them that they get a special deal on them and pass it on to the consumers. Most of these guns are fine and will give you many years of service. I especially like the kits that include the gun, video, and all the accessories that you'll need to start out. Only thing you have to buy are primers and powder. For $199.00, they are a good deal for any beginner.
I'd recommend a .50 caliber. .54 is overkill in my opinion and the recoil is not for beginners. And .45 caliber is a little weak in my opinion. Especially if the shot is marginal.