Re: Ah, but
"So If Samsung think their new SSD is going to compete on capacity with hard drives, they're going to have to sell it for about 8-10 times less than their current generation of SSDs. "
If they sell for 4 times the price of HDDs, most buyers will bite their arms off. That 3 year warranty is a good indicator of expected lifespan for starters.
Then there's the vastly reduced seek times, power consumption, size and massively increased bandwidth (mechanical drives top out at about 105-120MB/s sequential and drop as low as 5MB/s at 120-180IOPS random - and at that rate of sustained random IOPs large enterprise drives shake themselves to death in 6 months, let alone consumer ones.)
The introductory price of the 4TB QLC drives in "evo" format is unlikely to be above £600 inc vat - which puts them about 4-6 times that of NAS drives such as WDreds and I'd happily drop them into my 32TB ZFS NAS rig knowing that they'd save me about £75/year apiece in power bills alone.
Bear in mind that 2TB SM863s have come down from £2k to £1k, whilst you can get old stock 860evo 2TB for £435(M2)/535(2.5") and 970evo 2Tb M2 for £630 and the 860Evo 4TB sata being £880 (those are all inc vat) - these are all about to face runout discounts.