Price right now is completely disrupted by an anomaly in the market, leading to high uncertainty. But, before OpenAI decided to bring a wrecking ball to the market, a 128 TB SSD could be had for ~$13k. That's about $100 per TB, as compared to $15-$25 per TB for HDD storage (new ofc, with used, deals can be had but market prices are much more volatile).
These prices are a pipe dream now, but extrapolating from that market behavior, by 2035 you would be able to get a 4PB drive for, maybe, $20k. That's $5 per TB.
That aside, if you can get a $100 16 TB HDD, or a $200 16TB SSD, which one are you going to get? What about a $50 8TB HDD vs a $100 8TB SSD? Sure the SSD is more expensive but when you can drastically increase everything else at the cost of some capacity... SSDs will win out even if they do not reach price parity. If and once they do reach parity, SSDs will be a no brainer.
HDDs simply cannot compete with SSDs in the long run, even on price. To compete with a $20k 4 PB drive, a 100 TB drive would have to cost $250, and I doubt HDD companies can release new products and sink that low. Meanwhile, 2U blade servers will have 24 disks that each can house 96 Petabytes each. For a standard 26U rack that's 12x96 PB of data. The Exarack is coming in the 2030s, and by 2040, we might even be talking about the Exablade (1u server, 1000+ PB storage). :)
Let's see where this land though. Right now it is next to impossible to say where prices end up, and it could very well be that the hard drive prices stay high longer than the SSD prices... At which point, a $500 8TB SSD is looking a lot more appealing than a $400 16TB hard drive.