Ain't no reason not to buy a muzzleloader. But bear in mind once you start you may get addicted to shooting them. Like Forkhorn said an inline if legal is a good start. Most states require a .44 cal or larger and .50 cal if you plan to hunt elk or other game bigger than deer. You can buy an inline like a CVA Wolf that won't break your wallet and they are plenty accurate. But as far as price, when it comes to muzzleloaders, the sky's the limit. You can spend over $1000 on one that will knock the gnats off a fly's butt at 100 yards.
You can also get good deals on used ones too but be careful. Check the bores and any areas visually for any rust or pitting. Muzzleloaders need some TLC to keep in good shape.