I noticed when I go to upgrade my factory the upgrade costs start as if the factory size is 0, so If I go to upgrade my factory from 600 to 1200 cars. It seems to cost the same as building a brand new factory that can build 1200 from the start. Is that how it is supposed to work?
If you're talking about resize, then yes, the costs start fresh. We do not take into account the existing factory that is there.
I can revisit this at a future date now that factories are a little more balanced cost wise. At the time I coded it however, there was not much difference in the costs of a factory and the amount of money people were making. So it was set up to be more of a cost-sink, and less realistic.