A few things Bort has said about SAs in the various Q&A. Each point in the SA from 1-10 adds the same value to the SA. Obviously the SP cost increases. The diminished returns is applied to SAs over 10. Bort said raising an SA over 13 does not add much value. To me this means the penalty applied over 10 is logarithmic. Many things in the game are logarithmic such as training and SP levels so it would seem reasonable he was alluding to a logarithmic decay in the value for SAs over 10. The 40% bonus and penalty that catch reported was never confirmed.