Nightmare platform

Following the definition of a nightmare platform, I officially declare Microsoft Dynamics GP to be one of them. Sorry Dynamics GP guys, but I need an explanation for why I have spent half a day trying to figure out how this can be possible.

Consider this example :

salesItem.StandardCost = new MoneyAmount();
salesItem.StandardCost.Value = 1;
salesItem.StandardCost.DecimalDigits = 2;

salesItem.UofMScheduleKey = new UofMScheduleKey();
salesItem.UofMScheduleKey.Id = "EACH";

Policy policy = DynamicsWebService.GetPolicyByOperation("CreateSalesItem", DynamicsWebServiceContext);
DynamicsWebService.CreateSalesItem(salesItem, DynamicsWebServiceContext, policy);
 

And here is the error message :

A validation exception has occurred.
Validation Errors:
- StandardCost cannot be less than 0.

I'm still trying to figure out what amount should I put when the item has a cost...