I recall talking to the folks who built the Jupiter and 119 with OConner Engineering. My recollection is that in the late 1970s each engine cost about $750,000. Now that sounds like a bunch, and it is, but remember, they had to design those locomotives from the ground up, make all the blueprints, patterns and stuff like that as well as build the locomotives.
If someone is thinking of building a new narrow gauge locomotive, and one of the prototypes is still around, a whole bunch of patterns can be elinimated because some foundries use original parts as a basis for the pattern. I know. Been there, done that.
Likewise, just to have the actual locomotive available is a Godsend. In some ways, even better that a blueprint.
Finally, as to the cost to build one of these things. It may seems that say $1,000,000 is a lot of bucks, which it definitely is, but there are single engine airplanes out there that cost that. People buy those things every day. However, I might suggest an entirely different approach than some rich guy digging into Hip National Bank.
Over in England, there is at least one group I know of that formed a non profit organization for the building of a steam locomotive. They completed their project, and LO and BEHOLD they have a steam locomotive which they brought to Railfair 91.
The plan was that instead of asking for cash from different companies, they would ask for an in kind contribution of a part. That is, a wheel foundry contributed wheels, a boiler shop made a boiler, gauge companies contributed gauges, steel companies contributed steel, spring companies contributed springs, and so on. It worked for them, ain't no reason it couldn't work here.
Anybody want to build a particular locomotive?
Dan Markoff