I bid $5,150 for Job.pro but dropped out when I realised there were two bidders still in at $5,300. The third bidder didn't bid until $5,300 and eventually won it. I assume RegistryPro received expressions of interest in Red.pro and All.pro and that's why they were released to auction because Job.pro is a far better domain.
Other factors that put me off bidding more for Job.pro is the difficulty reselling a .pro for a profit if you pay over $5,000, the strength of the plural versus the singular for this keyword illustrated by the high sale prices of Jobs.com and Jobs.at which could make the plural a buyer's first choice, the relative lack of developed sites with JobPro in the URL which is unusual for such a strong keyword, and the fact that whenever you get an auction of more than one .pro, the strongest domain seems to end up selling for more than if it was sold with even stronger keywords. I paid $1,800 Loan.pro in September 2010 and I think it would have sold for more if had been auctioned on its own or with weaker .pros than Insurance.pro and RealEstate.pro.
I don't think there is anything inherently valuable about 3 letter .pros, it's purely about the keyword and the fit and association of that keyword with .pro. I picked up Cab.pro as a consolation prize on the back of my Taxi.pro sale. In the UK we say taxi not cab but two of the best known taxi brands are Computer Cab and Dial-a-Cab. Of the other .pros that were auctioned, Jet.pro is very brandable, I think that was good value.