They get this through debt issuance, primarily via land prices. Fiat money costs absolutely zero to produce, they give it out freely and in return you pledge to give part of your labour for 30 years.
If land prices were far lower we'd all be working 3 or 4 days a week. Employers wouldn't have enough workers. They'd be paying you most of the value you produce as they bid for you against other firms. And you might not work for them because you no longer have to spend most of your labour on banker tribute for the right to exist.
Land value tax is the answer. It would replace income tax, removing the regressive tax on labour and punishing economic rentiers.
I hope for the sake of my kids we can win this one.
http://www.henrygeorge.org/pcontents.htm
When people hear about LVT their immediate reaction is "another tax". Realise that it would replace income tax (or at least significantly reduce it at the lower end) and also it would reduce the massive tax via land price ramping.
Right now the banks are getting our tax instead of it being ploughed back into the state, via debt issuance. And producing nothing of value for it.