Unit price is not a issue

Flash storage has limit # of writing cycle. 100K times writing will kill the flash cell. Will you kill the flash before you upgrade the drive? Yes, you surely will. You will kill directory sectors and then your drive gone. Lot of user like defragmenting that even shorter the life cycle.

I will predict that future storage will be just the opposite way. Make the flash as the main storage and use disk as large cache.