Really depends upon how large you want your fleets to get. If the cost of facilities is high, then most likely your AI will spend more to obtain the growth that it is required to maintain. Sticking close to SEIV norm may or may not be the best thing.
In Facilities you could require the cost in Organics to be higher than other resources, and for ships the cost in minerals is higher than the others, while components cost about equal in all.
The choice is really up to how you want the AI to consentrate its resources, for production, or for maitenance. I hope this rambling helps, if it makes no sense, well thats just me.
