The companies apple subcontracts out to set up the production capacity based on forecasted demand. If apple ordered 30 million units, you can bet your bottom dollar that they would have set up more production lines to fill the order..
Considering how absurdly expensive the iphone 8 is said to be and how cheap alternatives are getting, apple doesn't realistically expect to sell over ~5 million units.. And remember, apple is the king of marketing - these "shortages" will make it seem more in demand than it actually is...
OLED is rapidly becoming the go to buzzword for 2018 mobile handsets (hopefully not just for so called flagship's).
This phone will cost at least 1200$