If you find that your cost settings keeps going back to 0 whenever you click on 'Custom Simulation Costs' on the 'Physics and Costs' tab, you need to change the regional settings for your operating system. The regional settings is located in the Control Panel. The name may vary depending on your country but it's where you change the settings for language, decimals and similar.
1. Open it and click on the button.
2. Change the decimal value to '.' without the ''
This is a bug in Visual Basic 6 which Darwinbots is designed with and not a bug in Darwinbots, so it's the makers of VB6 that should fix this. Go over and bash them!
Note that changing regional settings may cause problems for other programs that depends on this, like Excel for instance, so remember to change it back if you need to.