1. The "significant positions" are relative to the size of the company. Startup X's director of marketing /= Twitter's director of marketing. So the competence needs aren't the same and as a result the salary reflects that.
2.Funding levels aren't there to offer higher salaries.
There is no good answer to either of these.
I see stupid comments on here all the time like, "Well if you can't pay me 200k a year with unlimited vacation and healthcare and a 401k then you aren't ready for those positions." Fine, go work for Google and don't worry about startup jobs, that shouldn't prevent Startup X for trying to fill that position with those skills.
People also need a reality check. 110k is double the median salary for California [1], so if you are getting those offers anywhere else than SF you are making out like a bandit.
Their ownership is purely symbolic, in a relative sense, and it's a symbol of how little they own relative to a founder.
This is naiive. An employees risk is several magnitudes less than the founders across many factors. That said, some of the first employees get shafted on equity/pay and I think that is worth addressing, but again it is based on market rates. The other thing you can choose is to go work for a employee owned company if you choose.
[1]http://www.npr.org/blogs/money/2012/07/16/156688596/what-ame...