OK Andy I took a look at your two Mobile Devices corps on FB. Benita makes 170M/month (2B/year) and Richmond makes 200/month (2.5B/year). They are both fully upgraded and employ 300K employees.
Let's now compare them to your only Def Weapons Maintenance corp, Zerbst, and one of you Factory Maintenance corps, Martina (they're all the same). Both are fully upgraded, their product prices are the highest possible, and the slight differences in revenue are only a result of supply prices fluctuation:
Zerbst makes 600M/month (made 10B last year) with 272K employees.
Martina makes 750M/month (made 9B last year) with 263K employees.
I won't make any comparisons to Off Weapons Maint or Airforce Maint corps, as their products are very cheap right now.
So Andy as you can see there's something really wrong with the setup of Mobile Devices corps. Either supply quantities
Update: my CEO mobile devices are beginning to turn a tiny profit (<150m) not enough for me to actually build more, but at least its something I guess. I'll update if things change.