Hi SSShooter. If what you're describing is the bare receiver, with breech plug and trap door complete, less barrel the price quoted to you was way high. The last assembly as you outlined that I bought was $125.00. Oh, and that was with a good barrel. I think I'd look around some more. Might try giving old Red Daugherty a call, I think his number is already in the thread. If not let me know. 

I'm attaching the article that everyone is "quoting" on the bad threads and flying barrel. 

Dick

OOPS, guess the single picture was too big.     This one still tells a lot. More to come a little later.

Dick

Beautiful. Anyone making a double-set trigger and trigger guard like that these days?

The Rifle Shop will sell you a set of fit and hardened castings for $200, and cut your fly for another $59, but you have to buy their fly.  You just have to ask them.

Prices, complete Trapdoor actions should only run 125-150 at the most, if they are getting more than that for them I'm amazed. I always wanted to build one of these up and the method that Dick explains sounds simple to me. Simple is almost always better.
Mike

The Fix for the H& R trapdoor is to pin the Thumbpiece  to the round shaft of the cam  latch so that it does not rotate out of alignment. On the  H& R the alignment is  held with a set screw. On the originals, the thumbpiece is on a rectangular stud so there is no way it can come out of alignment. H&R took a little shortcut here which can be problematic. I took the rifle to a local gunsmith to drill into the round shaft of the cam latch but it was so hard he could not drill it. I sent it out to a shop down south and they fixed it. I tried swapping out original parts and they did not fit. 
The H&R rifles are great looking and great shooters, but this problem needs to be addressed.
The problem is fixable. Building a sporter with original parts is a much better option because high quality replacement parts are readily available. There are a lot of cut down original Trapdoors out there that have good bores, all you need to do is put new wood on or dress up the original stock. 
I hope this helps!
Joe S

I've repaired a couple of these "auto eject" re-pop trapdoors. First the problem lies in the fact that many of these have the rear latch that is not one piece with the locking lever . So you close the trapdoor, the outside latch snaps shut, but the rear latch is free to move and rotate. There is a set screw in them that can slip for lack of something better to call it. Repair?? None that works well. Answer??replace it with an original  trapdoor breech block. It takes some fitting, but works and ends "auto eject". Hopes this points you in the right direction.