William Greener, in his 1846 book "The Science of Gunnery", lists prices from his own gun shop. His guns were considered to be above average in construction and price for the time. For a high-quality double rifle, he charges 40 guineas, and for a single-barreled musket, one guinea. There were also shops charging as little as 1/2 guinea for a common musket.
In England, a gold guinea (containing 0.235 ounces of pure gold) per month was considered a good salary for a skilled workman or a cleric. A guinea was the equivalent of $5 in American specie.
So - for $5 you could get a cheap smoothbore musket FOB Birmingham; I suspect an American-made rifle was a bit more because the Birmingham shops were the most efficient in the world at that time.
Hope this helps.