A) you don't buy a used plane and modify it, like Donald Trump did with his Plane
B) the cost associated with Air Force One is not just for one aircraft, it for two, plus all the required infrastructure and support
C) Air Force One is not just Aircraft, it's everything The President needs to run the office in the air

The initial cost, of 1.4 Million, to first BUY a NEW Plane ... not a Used one like Donald did
Then you have to Equip that Plan to have the capacity to stay in the AIR for Long Periods of Time ... (Like Air-2-Air Refueling)
Then you have to Equip that Plan to NOT get shot Down ... like a Multi-Million Dollar Fighter Jet

.... the Hi-Tech list is way too long for a Donald Trump type brain to understand.
I think most people know what goes into building Air Force One and so does Trump. Whoever wrote the examples above though, I'm not so sure. He knows there are two planes and he knows that there are extra engines and that the planes are heavily modified.

He also knows that the initial cost was not $1.4 million but $357 million per plane, less if you consider that we don't get the plane set up for passenger flights. The multi million dollar fighter jet(s) are not included in Boeing's build price. Trump is right on this one.