Buffer have been incredibly transparent about their approach to this: http://open.bufferapp.com/introducing-open-salaries-at-buffe...
When I was a developer in a low cost of living area prior to moving to the bay area several months ago my salary was within 10% of the "Senior" engineer positions listed. This was at a non-profit, doing some really junior level CRUD work (so glad I'm not there anymore).
I'll leave it as an exercise for the reader to discern whether that means the salaries are "lowball" or not. And it's for Buffer to determine whether it can afford more, what the Buffer-market-rate is, etc. Nobody else. Frankly I wish more companies were transparent about salaries. Information asymmetry is a killer when it comes to negotiations.
I understand the cost saving benefit from an employer's perspective, but since that's not me, I've chosen my side.
Also, from a employees perspective if you feel you're getting a lower wage than someone who is of less value to the company, you can always try and renegotiate your salary.