Qualifying offer levels over the years:
2012 13.3M
2013 14.1M (6.0% increase)
2014 15.3M (8.5% increase)
2015 15.8M (3.2% increase)
It is based on the average salary of the top 125 players. Or roughly the average of the 4 highest paid by team. Average inflation so far has been about 6%.
The QO has been a little bit above the market rate for a 2 WAR free agent. Given that you can lock in a player for only 1 year (limiting the risk that comes with a multi-year contract) and get the draft pick if declined, I would think this should be offered to any player that projects to 1.5 WAR or higher. We should have offered it to Tim Hudson after the 2013 season. And should offer it to Aybar unless his performance level falls off the table.