How directly does the price per barrel affect pilot pay in the gulf?
You have oil and natural gas, you have drilling and production. Basically, oil and natural gas are more expensive offshore for a variety of reasons than on-shore oil and gas, especially with the development of hydraulic fracturing (oil sands are a different story - bloody expensive). When the price falls dramatically as it has, it can cost more to produce the hydrocarbons then you can make selling them - so some wells are shut-in until they become profitable.
Now and for the foreseeable future, on shore shale is plentiful and cheap so unless you have a huge field off-shore, it is cheaper to stay on-shore. It is not so much that off-shore helicopter pilot pay has dropped as the jobs have all disappeared. Bristow laid off 2/3's of its pilots over the last several years, I would assume ERA and PHI have lost substantial amounts of pilots as well.
On a related subject, you may like.
http://zeihan.com/presentation-clips/
(Top left video, The Reality of Shale)