Some big variations in spending estimates. I am single with no children and no rent or mortgage. I don't have much interest in holidays and in general my interests and hobbies are not expensive. I am reasonably good when it comes to DIY car and home maintenance. I have a home gym with free weights which I make good use of and which will last me a lifetime. I don't drink or smoke. My target spending for retirement would be 10 to 15k per annum (in 2015 euros) and I think that is generous.
In my view, cutting back on spending if possible (easy for me to say with no mortgage or rent) is key to this game. If you don't spend much you don't need to earn much. If you are subject to progressive taxation, the less you earn, the greater a percentage of your gross that you are left with after tax. In terms of investing, the less income you need, the less capital you need to generate that income. You can also invest conservatively rather than having to chase returns with risky investments.
My career progression in the public service has hit a brick wall and I am increasingly frustrated with the chaos, unprofessionalism, bad customer service and incompetent management that I witness every day in my workplace. I am regularly thankful that I have savings and an ability to live relatively frugally as I have potential options to retire early, work part time, take a lower paid job and so on - options that the average wage slave doesn't have.