There's no need to buy an expensive entry level rifle, although it is a matter of choice and personal preference.
There's so much to learn about shooting and cleaning a muzzle loader, not to mention all of the accessories needed, that new BP shooters can sometimes get disappointed about sinking all of that money into a gun before they know whether or not they will even like the sport.
There's modern and traditional muzzle loading. Traditional is much more fun for plinking, informal target shooting and ease of loading, while the modern guns are more for long range precision hunting and target shooting. Not that traditional can't be for long range shooting too, because in international competition it is. In the end it's more often about the length of the barrel, barrel twist rate and form of projectile.
But the point is that it's nice to be able to enjoy both (if you find that like it), and if you sink most of your money into just one end of the sport, then you might not consider buying 2 guns to enjoy both forms of the sport, so why not just buy one less expensive gun so that you don't lose out on a good portion of your investment if you find out that you don't like it?
Plus, the inexpensive inlines can often function & shoot just as accurately and provide just as much enjoyment (and heartache) as an expensive gun.
So the measurement of muzzle loading enjoyment isn't always in direct proportion to the amount of money invested.
Sometimes it's quite the opposite. The less money spent the better, because some guns and their performance and maintenance issues are totally unrelated to their initial cost.
Some cheap guns are just more ergonomic & enjoyable, and sometimes some forms of muzzle loading just isn't enjoyable for some people, no matter how much is spent.
So, I'd suggest to start small and work your way up so that you don't become disappointed soon after you emerge from the starting gate.
Sincerely, good luck with whatever purchase you decide to make and I hope that you have lots of fun making gun barrels belch lots of smoke!