10kg of steel would cost about USD$10.00, and then shipping it around the world costs again. At my factory, we use the number "50 cents a pound" as an average cost for shipping pallets around the lower 48 states.
So your extra 10 kg would cost me about $20 more. At retail that would be another $100 or so. In other words, making it 10kg heavier would sharply increase the price; it would also be for things that aren't easily visible to the consumer. Your competition would destroy you.
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.
I seen an article on the ring pulls on top of coke cans. They are hollow because it has a huge impact on raw materials usage (over the course of 10 million cans). I think every gram counts to the bottom line of the share holders no matter how mundane. Similar to the UK Construction Industry. Hit the minimum possible legal requirement and charge the maximum amount of money.
> They are hollow because it has a huge impact on raw materials usage
It's been a while, but I remember when the transition from pull tabs to "pop tabs" occurred; at first (IIRC), the "pop tabs" were solid, but it wasn't long until they became hollow as well.
Of course, that led to some problems which still exist today (though not nearly as often). The biggest one being the balance between the strength of the tab, vs the opening part (whatever it is called - closure?). In the past (and occasionally today for the odd soda), you could pull up on the tab - and it would bend or break off, without opening the soda! Simple enough to fix (do not press down on the opening with your thumb!) with a butter knife or some other similar tool, but annoying at the same time.