0.74 has cost calculator implemented, and working - base cost from chassisdef + equipment cost + MechStatisticsConstants.json::CBILLS_PER_ARMOR_POINT * totalArmorPoints, rounded up to 10k alignment results the same value stored in mechdef.json, as I tested. So, after exporting a loadout to .json internal game mechanics should process it further properly.
To observe this run Mech Designer in advanced mode, expand the right side to show "Tags and Description" data, and watch "Mech Cost" field.
I left possibility to manually edit the cost in case of someone would make a mech cheaper/more expensive.