Trello (like FogCreek and StackOverflow) has a very regimented salary process that Joel Spolsky has talked about publicly here:
http://www.inc.com/magazine/20090401/how-hard-could-it-be-em...There are a few elements of it:
1. There is a set salary table based on objective factors (e.g. years of full-time, professional programming experience). Your salary is 100% determined by that table and isn't negotiable.
2. The table gets updated every year for market factors. Everyone gets a raise if the market moves. You get raises by progressing through the table's objective criteria.
disclaimer: I am an engineer at Trello and we're hiring: https://trello.com/jobs
I have had a lot of visibility of developer salaries in previous positions (ran development and hired devs at 3 startups) and I spent a year as a developer evangelist (in recruiting). I found the Trello offer in line with my expectations of salary.