Costs.... Hmmm.

Things I couldn't make:
Barrel blanks from the States 11 off (1 spare) about $40 each I think
Gear wheels from the States 2 off about $50

Things I paid for:
Metal for rails 20 pounds
Springs. I priced them up at about 70 pounds

Things I procured:
All other material was courtesy of work so no cost.
All castings also courtesy of work so no cost.

If I was paying for material and casting I'd be looking at a couple of grand minimum. If you machined everything from solid rather than using the facilities at hand it would bring the cost down a hell of a lot. Materials are probably still a good few hundred pounds though.

There's not much to see at the mo as it's all the smaller bits I've made, but once I have the castings back, you're welcome to swing by and have a look. I'm near j3 m25