Need more specific numbers for prices. Skipping item A at first sight is probably better.
For example, an hour worth of item B could mean anywhere between 1.9m and 2.8m. impossible to do accurate math with retarded ranges
EDIT:
for the sake of it if i were to use the average of the price ranges you listed.
Gathering item A is worth ~250k /hr
Making item B is worth 2.35m /hr and costs either ~750k or 3 hours of time.
This means B is worth 1.6m/hr if buying A from GE.
if you produced A then made B, it would take ~4hrs for 2.35m profit. thats ~600k /hr
That means Gathering A is a waste of time/money
Making item C is worth ~10m /hr and costs 1.8m + either ~4m /hr or 1.7 hrs of time.
This means C is worth ~4.2m /hr if buying B from GE.
If you produced B then made C, it would take ~3.7hrs for 8.2m profit. thats ~2.2m /hr
That means Producing B is a waste of time/money
Might be completely fucking wrong, idk and idc