Are washing machines not still being made with concrete in the base? I'm sure balancing has gotten more intelligent, but there still needs to be some mass to keep the thing from walking.
Of course if that 10kg of steel was on the drum, the stationary mass would need to be increased as well. But I doubt washing machine drums are really a high failure part, so a hypothetical "10kg of steel" is a useless in the context of a washing machine.
It's hard to make a comprehensive argument about entire machines when the problem is designers having a principle agent problem for every single part.
Of course if that 10kg of steel was on the drum, the stationary mass would need to be increased as well. But I doubt washing machine drums are really a high failure part, so a hypothetical "10kg of steel" is a useless in the context of a washing machine.
It's hard to make a comprehensive argument about entire machines when the problem is designers having a principle agent problem for every single part.