I do agree with Thomas. From the pics, it looks like one would have to also cut out the Rudder and create its leading edge, then build a "tailstock" on the fin. If one needs to skin the wings, then one will likely have to do the same for the Htail (I'm assuming).

Then, when you get to the wing, even though its a moderately tapered wing, there's a lot of high lift stuff on that wing. So one will be cutting out the (split brakes), the flaps (its probably a slotted fowler arrangement, but we can keep it simple for the early birds), and that is ignoring the LE devices. Spoilers?

If one were to apply a $10 per hour rate on this, the cost would still likely be quite high. Depending on level of detail. And 120" models get quite large to have to move around. I think you did mention the fuselage could separate...

With my Fitter project I just wrapped up, I shudder to think what the total labor cost would be, $ rate X manhours...

One could also throw out a number $ to build one of these kits, flat rate, but I know I'd have to see what hardware (structure) is involved.

These parts would make a great "blank canvas", though, so to speak, to make a very nice and impressive model.

Edit - added: Also, when models get large like this, I think it's only natural to make them more scale functioning than a 5 foot span model. It will be noted if things like spoilers, slotted flaps, even slats are not there.