Here's a presentation of a comprehensive NREL study from 2018, but I don't know the source of the numbers. It finds hydrogen and flexible generation (that is, natural gas turbines) are best for long duration storage. Notice the slides on page 13. PHS is way out of the running for the storage case being discussed here; it's not close.
Thanks. I mean it’s from 2018 and that is ancient history as far as storage costs are concerned. But yeah those $/kWh numbers for PHS are orders of magnitude higher. Thanks for the link, I’ll try to find the final study tomorrow
https://www.nrel.gov/docs/fy21osti/77833.pdf