Stacking all your economy or manufacturing bonuses in one place is a bad idea in general. The reason for this is that there are soft caps on both based on planet quality, and once those are hit it takes a lot of effort for a small amount more gain.
That is, say you have a class 24 (post-enhancements) Earth, which has a base production capacity of 100IU. With its various wonders and regular buildings and the nearby starbases you have a manufacturing bonus of, say, 400 percent, which isn't at all out of the realm of possibility. This means you'd expect to be getting 500 IU out of it, of which 1/3 of the bonus, or 133 IU, would be free. However, because of the caps, you're likely to be closer to 325 or so. The reason: bonus production is capped at 3xPQ for a total of 72 IU, and paid production at 10xPQ or 240 IU. 72+240=312...but the caps are soft, and so the added bonuses past there might get you just a bit further.
-EtherMage
~SDC~