Board Thread:Questions and Answers/@comment-25054973-20140727143736/@comment-35190615-20140727151458

It seems to be a ranking of the aircraft. It seems that each aircraft in a certain column of the tech tree will have the same "Cst" score. For example, the F-22A, T-50, F-35B and SU-47 all have a "Cst" score of 750, while the Typhoon and F-15E have a score of 650. Each column is differentiated by 25 score, hence, why the F-4E has a score of 350 and F-16C has a score of 375, and so forth.

I hope that explains it.