There are several for sale now in the $400+ range. They have been selling for around $275 to 350 in 95% condition in .45 caliber but the best way to determine actual value is to search the on-line auctions, such as gun broker and auction arms or even proxibid enter your details in the search and see what is selling and for how much. You can also search the archives and or sold items to get an idea of what your gun is selling for. Another place to look is The blue book of modern black powder values, available from midway USA and blue book publications as well as many of the other hunting and firearm stores. Also available to NRA members on - line for free on there web page. That will give you an idea of the general value. Guns tend to have some regional value too, say a Thompson Center Seneca may be worth a bit more in the north east than in the mid west, and a Ruger old army may sell higher in the northwest than the east coast. Don't forget condition has allot to do with value, and with black powder the bore is king. You may have a gun worth for example $500, but the same gun with a bad or rusted bore may only be worth $150 so compare apples to apples.
200
50-200 usd
100-450 or so
100-500 USD
400
Depending on EXACTLY what you have; a few hundred to tens of thousands of USD.
Depends on who shot it and or who was killed with it!
50-300 USD or so
1gran per caliber
50-500 USD or so depending on specifics
Anywhere from $50 to $25,000. Depends on which gun. Caliber 45 refers to the size of the bullet, and nothing else.
100-200