Depends on what you want to do with it. The most costly scenario is your obtaining an after-market drop-in barrel. A LOT of guys if they find an inexpensive TC such as yours, but with a roached bore from improper cleaning, send it out to get the barrel reamed smooth in the next higher common caliber. So a lot of .50's become .54 smoothbores (28 gauge), and a lot of .54's become .58's (24 gauge). Normally these are plenty accurate for deer using roundball out to 50 yards, AND do well on squirrels and rabbits with shot, and this is often done for less than $150 including shipping. For a bit more one can have the barrel reamed and then re-rifled, if one needs to go for deer and such beyond 50 yards as a regular rule.
LD