Both the number of cups of coffee you get out of 200g of Nescafe and the number of washes you get out of 1 kg of washing powder will vary (depending on how you strong you like your Nescafe and how dirty your clothes are). The same is true for deodorant or shower gel. I think weight/volume measurements are fine for almost everything.
Packages for things like dishwasher tabs usually have a number on them (in addition to weight/volume, which is mandated to be on the packaging).
Packages for things like dishwasher tabs usually have a number on them (in addition to weight/volume, which is mandated to be on the packaging).