You can take a look at the market reports from the various brokerages and the MLS to find data about sales. Vanguard, Paragon, Marcus Millichap, Colliers, and etc all offer market reports.
Like what others have said in the previous posts, the sold price is what matters and comparing that price with what similar buildings have sold for already.
Plus, the 69 Clementina building is located literally right next to a freeway exit/entrance to and from the Transbay Terminal. Unit #502 is going to get the blunt of the noise because it's at the same level as the freeway, which is only about maybe ~50 ft away. I rented out unit #503. The unit has no parking and the building is located in an alleyway. Compare this property with Hawthorne, Parc Merced, Blu building, 77 Dow, Metropolitan, 74 New Montgomery, and etc and you'll see that there's a very big difference.
With that said.... It's always a good time to buy and sell ;)