Except for the fact that it has a non prototype set of lettering that reads "Union Pacific", the ONLY similarity to that engine and an FEF [of any class] is the 4-8-4 wheel arrangement. I have seen this engine offered for sale before at a similar [or higher] price. The family is very impressed with their own [alleged] lineage, as well as the skills of the builder. From the text description, it is clear the seller knows little or nothing about model engineering. At best it is a crude model, no matter the quality of the machining. The price is about $125,000 TOO HIGH.
As usual, just my biased opinion based on few facts and lots of observation.
Based on recent auctions at ME shows, 25K (20K for the loco, 5K for the cars) is not unheard of, especially when the bona fides of the builder as a competent ME is unknown. 5200 ft of aluminum rail [1/2 mile of track] (used) is still only worth marginally more than the scrap price. So, I think we are still less than $30K. Can you buy to Aster C&O H-8s for that?
Seems to me that true story line; instead of ebay sell your train items at Barrett Jackson (even with the commission) given the high end customers that are drawn into the "big show" under the big top for any thing that has wheels (as event by the 12 foot three wheeler with the hemi engine).