My company meeting to San Francisco has been cancelled, but I've still been following the hotel prices for those dates on the Amex FHR site, since I knew what the previous numbers were like.
The only hotel charging more than $500 per night (for the lowest available room) is the Four Seasons at $523. When I booked in January, this was an almost $800 room. Ritz Carlton was full, but now has rooms at $499. Fairmont and Palace were $450+ and are now $229.