No problem to make lots of an item, just size the production facility approiately. Big issue is selling those, and I don't think that will be an issue. Just look at the diverse roup on this forum. We all find it apealing for many different reasons. The most telling is cost vs ANYTHING else and MPG vs ANYTHING else indipendent of price. There is no competition! And notice the 250000 units are built in 2 shifts on the same equipment. A good engineer plans for contigency, low sales = 1 shift, sales meet projections=2 shifts (as stated) and GREAT sales = add a 3rd shift(or work overtime).
I have experienced an engine development program. I am fairly certain that the castings shown are far from the only castings. Casting development takes several(to MANY) interations of cast it then machine it and measure it. That is done in private because the first few times don't go as expected, thats "development". Wall thicknesses need to be confirmed, passages verified, ect. The engine will have run many hours and interations on a dyno/hot test BEFORE anyone in the general public is informed that "the engine is ready" Quit worrying about it, when it's ready he'll unveil it! They are not going to show us the engine until it is proven. How would folks react if they said "hey we got an engine ready for dyno testing" and it failed at 5 hours???? (thats not unusual) That is exactly what has to be avoided. Nothing works perfectly first try, I am sure ,from past experience, that there have been many castings machined and assembled. When the final rendetion is validated we will hear and NOT before. Lots of concurrent development going on, this is not like building a gocart in the garage where you have to do everything in sequence all by your lonesome.
By the way, we build 1000 automobile engines, from casting to ready to hang a trans on, in one 8 hr shift, no big deal