Seldom exceed 150 USD
10-100 USD. Yes, any of the major wood shops should be able to make one.
50-100 or so
Single barrel, tops out at $75. Double-barrel, tops out at $175. email@example.com
I believe that King Nitro was a model name of Shapleigh Arms Co, St. Louis, MO.
You have already identified it as a Shapleigh's King Nitro. Shapleigh Hardware was in St Louis Missouri from the mid 19th century until the middle of the 20th. Their King Nitro guns were manufactured by W.H. Davenport and later by Stevens/Savage.
BLue Book of Gun Values