The cost of the 1200mm, like the cost of all the other supertele primes, is all about the amount of glass.
Glass is melted sand. Glass is cheap -- even cheaper than a silicon wafer. Even fluorite is cheap and abundant.
What costs money is first the R&D; even Canon's very intelligent and skilled and very well paid engineers with all the equipment they might want at their disposal haven't yet truly figured out DO in the first place.
And what next costs money is the tooling. So you've got a bag of sand. How are you going to sinter it with the right trace elements into a bubble-free block the size you need? How're you going to grind that into the shape you need to the tolerances you need? How're you going to make however many thousands of these elements you need for the lenses you're going to sell, and where're you going to keep the individual machinery you're going to need for each different element? Or, how're you going to make a general-purpose lens manufacturing machine that can handle a broad range of the very different elements you need?
And let's not forget the housing, autofocus motors, IS gyros, and circuitry / firmware -- very little of which can be reused from lens to lens, especially with the big exotics.
Now, take the cost to make all the machinery -- again, the materials are a rounding error -- and divide by the number of lenses you expect to sell. Add in all the salaries you have to pay, all the taxes, all the shipping, all the environmental cleanup fees, all the rent, and a few pennies for the shareholders.
If you're going to sell lots of these lenses, you can spread that huge cost over all of them and wind up with a rather modest sale price.
But if you're only going to sell a few thousand, as I expect is the case with the Great Whites, then you have to make each buyer pay through the nose to offset all of that.
Think about it for a moment.
Do you really
think that a 1200 is as expensive to make on a per-lens basis as an exotic luxury sports sedan? Or that a 400 f/2.8 costs more to make than an econobox?
No -- of course not!
But the sales volume is so low for the lenses....