Can I have several SB's in one sector that give multipe bounus? For example, 3 SB's in one sector all the with trade and manufacturing bounces maxed out. Will my plants in that sector get all 3 bounces?
Yep, the bonuses will stack. Just remember that above the one-time cost for every constructor needed for improvement, each starbase costs 10 BC to maintain.
The bonuses stack, but at 10xPQ you start to take penalties of extra production, so you're not going to get much more production out of maxing dozens of starbases. Trade is not caped, however.
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