There is a way, yes. It's not "easy" to setup, but of course once setup it's very easy to use, because it's all automatic.
This is detailed in the User Guide (section 31), but I can put together a config file for you. With the way you have it configured it will be rather verbose. Seems like there might be a better (formulaic) way to compute those values. Did you use percentages for prize values originally?
The config file is attached. Save it. Then on the Prizes tab press the "Automatic" button, and then the "Configure" button. At the top press the "Change" button and select the saved file. You should see the prize levels that match your description. Press the "OK" button, then check the "Enable automatic prizes" box and press the "OK" button.