It is, and I can give you some real numbers in fact: http://www.itjobswatch.co.uk/contracts/uk/full%20stack%20developer.do ￡400 per day, on an average of 20 days per month, 10 months per year would mean ￡80000 per year before tax, so around ￡64000 per year after tax if you know your way around the contracts and terms.
This is the average. You could be under, you could be above it. The conclusion is that you can, based on the numbers.
It all boils down to learning to 'play' the market. You need to anticipate what frameworks and technologies will be in demand the next few years, and what clients will use them. You will need to learn how to sell yourself as a company asset to your clients.