Yes, but it also usually has declining marginal cost across most of the curve. It's complex. It definitely gets expensive at the margin when growth requires new plant, but the big problem is when growth is unpredictable and may end; SF has a pretty safe long-term growth plan built in, so making 100 year investments (at muni bond rates!) is safe.

I just don't see even 100k rich non-services-intensive people as being likely to cause a problem. What SF should do is get rid of the previous stupid payroll tax and Ron Conway/Ed Lee's even worse gross receipts tax and institute an income tax of n% on residents or those working in SF. Maybe make it progressive (just set it as x% of someone's California state tax bill?, maybe +10% so it'd be about 1% of gross income?).

Then, having 100k people making ~$300k/yr (reflecting capital gains plus wage income) and consuming <$100/yr in city services in some towers along the eastern side of the city would be awesome.

$300mm/yr in extra tax income would do a lot.