Eventually, they price / strike themselves out of a job.

Think ship building, car manufacturing, ship building, newspapers, then the Marxist union morons move on to their next target.
My younger brother, used to work for a local paper who did their own printing. Militant union rep and his senior brothers caused all sorts of trivial disputes. My younger brother could see the writing on the wall, local paper sold out the national printing group, who kept local journalists and closed the printing works.

Bob Crow is always calling underground drivers out on strike 23 in 4 years. Boris Johnston has had enough, his aim is to have the whole network automated ASAP, Northern line will be by 2014 and most other lines by 2018, so no drivers required.
http://www.telegraph.co.uk/journalists/rowena-mason/9166138/Boris-Johnson-to-challenge-unions-with-driverless-trains.html