Ah zeno's paradox. When the SSD matches the HDD price, in 28.5 months, the HDD will have moved, and so on and so on. Although at some point they'll probably just make many many fewer HDDs so the price will stop moving much.

For any storage experts, will HDD still be preferable for long-term cold storage or are those even currently an unacceptable solution? Seems like cold storage might end up being more important over time. I guess AWS Glacier is <$1 per TB per month which is pretty cheap and can presumably even fall over time. I have no idea what the reliability of these services is though.