A pool with 30% of mining power may have an incentive to do this. But increasing fees means the pool with a 10% share increases its revenue without doing any work. So, in an ironic twist, this should prevent a monopoly forming? Its better to be the 2nd biggest mining operation, and let #1 push up the fees.
but there are no pool with more than 17-18% for now, so how can they do this attack? are the pool working together to do this and then split the profit?
if this is the case, this is really a miners's monopoly, chinese miners working together to screw bitcoin is an understimated issue, they can also perform a 51% if there will be a real reason to do it
higher fees means more miners. These new miners do not want to be part of the "monopoly", but do want monopoly prices.