The Lehigh bare primer plug for the Knight DISC Extreme is under $50 shipped. So total (with shipping) you would have about $450 in a DISC Extreme with a Timney trigger and Made in the USA. If you want a cheaper rifle look at the CVA Optima V2. Its well under $300 and a good rifle for that kinda money.
https://www.muzzleloaders.com/produc...-muzzleloader/

You need both of these parts to convert the Extreme to bare primer. About $31 + around $8 to ship. Add another $22 if you want a extra pack of vent liners and you are set for many years of shooting.
https://sskfirearms.lehighdefense.co...product_id=258
https://sskfirearms.lehighdefense.co...product_id=259

4 extra vent liners. The breech plug comes with one.
https://sskfirearms.lehighdefense.co...product_id=282