A good original 84 model trapdoor goes for about a grand. As far as I'm concerned they are a real bargain . If you get a Trap door you will want an 1884 model as they have the Buffington rear site, which is windage adjustable. There is an outfit called Trap Doors Galore, that often has a good selection, but he is REAL PROUD of them. It is a good place to look at the different models and comparative price. There a lot of good 84's out there. They were National Guard guns and did not see much use. If you have more interest in a TD. let me know, and I'll give you a TD 101 class.
If you buy a Repro, it will always be a repro. Shoot it , modify it, enjoy it. If U buy an original, you will have a shooting collectable. BUT, you also have the responsibility to preserve it for the future. You do not own an original, you are only it's care taker. That means no tang sites, scope mounts, sanding the stock, re blueing etc. I have several original's, and I shoot my originals, but they don't go out in the rain. They don't get tied to the 4 wheeler, or thrown into the boat. For that I have repos.
The highwall is a wonderful gun. It's rugged, accurate, well balanced, and comes in many calibers.
Don't discount the Martini Henry. Atlanta Cutlery has them. They found them in an old armory in India. Get a beat up one and re barrel it, to a more useful cartridge.Or keep the original barrel, and sleeve it. I know that this goes against what I said above, but the MH's are in pretty rough shape.
I have a rolling Block action that I plan on turning into a rifle this spring, if $ will allow. They are all great fun. But it will be heavy, cuz I have to have a 1 1/8" barrel to get it to fit the action.
Decisions, decisions. So many fine rifles, so little time and money. Don't even start to look into British single shots or double rifles. That is a real expensive bug to get bit by!
Go to the Black Powder Cartridge forum for more info. on the different rifles.
good thing they can shoot! 
