Do people really want to go to Japan and see this? I mean if you are already in Japan for a business or even vacation reason you could maybe see this as an extra thing, but how many people would go to Japan just for this? I doubt that number could be huge, it would be very minuscule and considering they have spent billions on this, I doubt that it would recoup the investment.
Obviously you could sell your know how and that is another subject but that is not the reason why anyone would build something for once, that has to be repeat and have to be something you constantly do, if you do it just once how could you have such a huge know how, you did it and it is over, but if you do it multiple times you would know it better and what could happen at the same time as well.
Well unless you are a hardcore fan then most likely very few people will actually go to Japan just to see the gundam, however now it is an additional tourist spot, after all in what part of the world can you see something like this? Nowhere except there which is one of the main reasons people travel, to see other cultures and their monuments and attractions.
I tried to find how much this cost but I could not find it, however regardless of it I think they can eventually get profits with this not only as a tourist attraction but do not you think that many people will be interested in the knowledge the engineers have amassed during their work? That information is worth a fortune if they know how to exploit it.