>The cost of fielding AP ammo vs the cost of armor would make it essentially useless
This is a retarded perspective, tbh. The armor plating itself wouldn't be the cost-prohibitive part of the suit, honestly that stuff's pretty cheap, relatively speaking. The same cannot be said about the mechanical and electrical/computerized components (and probably the future-magic power supply) that would make up the exoskeleton, that's were all of the cost comes from.
If we were going to invest in these exoskeletons, there is no reason why we shouldn't add a little extra coverage of level III -IV plating that wouldn't be viable without the suits assistance, at least not for any reasons of cost. The mere fact that the amour CAN be defeated doesn't eliminate all of its' possible tactical benefits. AP rounds are not what you should be worrying about, increased survivability against mortar and artillery fire is what should be making your dick rock hard.