A not inexpensive Big Boy's Toy by any means.
I think I read a report that the majority of parts needed to restore it the first time, had to be re-manufactured as there were no stores, molds and 'patterns' along with the Blueprints available which took time to make and added more cost to the restoration.
A beautiful thing to see running as it was built to do but for the unwary, it could be quite an albatross hanging around the neck.
The NRM will easily make back the £2.6m spent on the
Flying Scotsman overhaul, it's a very profitable locomotive to operate. A fair proportion of the funds for the overhaul was actually raised by its operations in 2004-06 after some interim repairs got it back on the rails for a couple of years before the full overhaul started, so they already have a head start.
The NRM aren't fools - they know that
Mallard is not as viable to operate as
Flying Scotsman and so it is kept in a condition only one step above 'stuffed and mounted' (i.e. it can be towed around by other locos - in the last case by
Tornado) at the museum.
Note she is currently running with 60103 on the smokebox door, 502 on the RH cab side and 103 on the LH cab side...
Once the test runs are completed, the current hybrid livery (the plain black from WWII without nameplate and 'NE' on the tender, with the LNER 1946 numbers on the sides) will be replaced with the full BR 60103 livery.
The NRM decided on the BR livery instead of the more famous LNER version to maximise the historic accuracy, as the French double chimney and German smoke deflectors were only applied under BR ownership.