Re: return
A city having no electricity bill for its street lighting sounds like return to me.
Trying to get some numbers to go with that notion didn't yield much, but a BBC News article on the City of Westminster running their street lighting at 75% on average mentioned it would save UKP 420.000 on their leccy bill. Westminster is very very roughly 1% of Chengdu in area, but it's probably lit more brightly than Chengdu on average; let's say four times as bright, for ease of calculation. So taking that amount saved and multiplying by the difference in area we get about UKP 42 million, without correcting for energy price differences between UK and China. This would not quite pay for a single Space-X launch, but it's in the ballpark. I expect you'd need at least a few of them to get the materials plus an assembly robot up and into geostationary orbit.
If this guy has designed a really lightweight mirror it miiiight work.
Biting the hand that feeds IT
