I think that is too optimistic. The cost / capacity of NAND, even by Western Digital roadmap wouldn't have come down to current HDD price by 2027 / 2028. And that is assuming HDD price dont fall.
I agree. The price difference between SSD storage and HDD per TB is still a multiple (seems to be currently about 5x). That is better than the 10x it was a few years ago; but I don't expect them to be equivalent any time soon.
Making sure I'm looking at new hard drives, I see prices around $15/TB at the cheap end. There are a few name-brand SSDs at $45/TB, many more at $50/TB. They're not high end but even the low end is fast these days.
Although the ads I saw claimed to be new drives, I have no way to verify that they are not refurbished. Of course, I don't know if the $50 per tb SSDs are reliable either.
It seems that HDD density has stopped improving so fast and you're going to run into a wall on price reduction because due to the extra material and shipping cost involved in producing an HDD vs. a tiny m.2 SSD.