[douglas]

Say you have mineral freighters that cost 10000/2000/0 to build and 10 colonies with 0/2000/1 mineral Launch Pads building them. Each colony will produce one such freighter per turn at no minerals cost. Each turn, assuming safe routes and after the first freighters from each world have had time to reach the spaceport, you will gain 10000 * 10 * 1.1 = 110000 minerals from scrapping freighters. Assuming resource costs in general are on about the same scale as stock, that's quite a substantial income, especially coming from just 10 planets.

The overall rate of income is per Launch Pad and can be easily scaled simply by changing the build cost of the freighters. In fact, you don't even need a scrap return above 100% at all, since the build cost is never actually paid anyway. It just needs to be sufficiently higher at a Spaceport than at a Launch Pad that it's almost always worth taking the time to send the freighter to the Spaceport before scrapping it. Also, you could have technologies that increase the effectiveness of your Launch Pad-based mining by giving more expensive freighter hulls or components. The extra cost is never actually paid and does not affect build times, so it only affects the gain from scrapping.