The cost hasn't been cited in the "invention", but concrete is something that weights roughly 2,200 Kg per cubic meter, and has a cost (of course it depends on

The cost hasn't been cited in the "invention", but concrete is something that weights roughly 2,200 Kg per cubic meter, and has a cost (of course it depends on where it is produced) of less than 100 US$ per cubic meter, the 25 Kg counterbalance costs between 1 and 2 dollars, and is probably just barely comparable to a mass produced injected plastic tank, but I doubt that there will be any actual savings by the manufacturer. And there is no real "visible" added cost of transport. A 70 kg washing machine is typically 0.60x0.60x0.90=0.324 cubic meters, let's say 0.7x0.7x1,00=0.49-0.50 including packaging, it has a a very low "density" of 70/500=0.14. On a truck with a platform of 2.40 m x 13.00 m (a normal large truck with a loading accepted of around 30,000 Kg ) you can usually put (in two levels) between 100 and 110 washers (2.40/0.7=3 13/0.7=18 2x3x18=108). So you have this big truck, designed to carry 30,000 Kg and you load it with 8,000 Kg instead. Do you think you will get a discount from the trucker? And do you think that you will get a further discount if the load is 5,000 instead? As well, do you think that you will get a discount from the delivery (and installing) guy if it weights 20 Kg less (but the guy needs to remove the top cover, fill the tank, re-assemble the cover)? From an environmental viewpoint there are undoubtedly savings but the manufacturer (or the customer) won't be able to appreciate them in practice.