I am a Computer Hardware professional. I started working with computer technology in the early eighties. I have seen the evolution of technology starting with closed platforms like the game console era and then the move toward open platforms like the Home Computer Golden Age. In the last 5 or 10 years, I have witnessed technology changes that are slowly moving away from open hardware designs towards hardware that is locked down and can’t be modified by the user.
Presumably the demand isn’t there, £1200 is a lot for a consumer drive and spinning rust is 1/3 the price.
Demand might be low, but on the other hand the cost to develop and manufacture a run of the drives may not be too high either.
I do have to say the increase in flash memory prices haven’t helped. A year ago I bought the Samsung 8TB drive for $300 (US). If they had a 16TB model for $600-$700 I would have bought it.