I found exactly the same in my situation, you reach a peak and then have to move to something else otherwise you stagnate and lose against inflation.... Still fighting that battle....
In some cases the companies will offer up to 30% increase to your last package, but because of what you are earning, they want to make use of the "cheap" labour that they are acquiring. This norm is also in Gauteng starting to filter through.
I have spoken to a number of recruitment agencies about this exact statement. Their explanation is that if they don't submit the details, then companies will just ask for recruits that do submit the detail. It's a vicious cycle. The best I got so far is a 25% increase when moving, nothing market related yet. The only effect to this cause is that I will keep jumping until I find something market related and risk being called a job hopper.... It stays a catch 22.
The only way you will make real money is if you can afford to start something of your own and for that you need money or investors willing to part with their money on your risk profile. Bottom line is you need money to make money, a commodity which employees don't have.