Experience/costs...yeah, balance is undergoing heavy rework for next version lots of long hours have been spent staring,changing and rearranging them. (and are still in fact being spent *rubs eyes*)
As for Iphkrates read their description and you will find out why since there is included much history in descriptions of the units.
edit: That version that you use, which one is it? 1.0? 1.1 is available for download by now check download section
Reason I am wondering is the faction colours have a tiny difference I see but it could just be a trick of the light when compared to this picture (but then this picture is an early preview of the next version)...