Each units performance is balanced around its Cost, not what ones payes to get it. Thus:
Commandos cost is 350
fallschirmjager cost is 380
Stormtroppers cost is 270
Commandos actually perform quite well for their cost given that they come with camo, one of the strongest grenades, can be equipped with 2 of best LMGs or 2 Piats, demolition charges and are one of most cost efficient ambush units...
New 222, M3 vs WC41, USF M1919 vs LMG34 vs other LMGs, Piat vs PTRS, penals vs rifles, ISG vs 120mm, shocks, paras with thompsons and rangers with thomsons and possibly quite a few others beg to differ.
Also, infiltration commandos(new 4 man squad) should be hands down strongest infantry unit in game without any 1v1 competition.
Yes, I've put there units that don't have premium costs for building/call-in, but these are good examples of balance vs cost being far off, rangers vs paras being one of most obvious examples.