In Australia the misleading part is what's actually weighed. The price per kg for canned beans doesn't help when 400g supermarket brand is 280g beans, 120g water. :(

But on average, with pretty much everything else, it works just fine.

In Italy, canned foods must display a "dripped"(?) weight, that is the mass of the contents after the oil/water/whatever has been poured away

"Dry weight" is what you're thinking of.

Then they start injecting meat with water and dye to make it heavier and more eye-pleasing.

Yeah, but is the dripped weight the one being shown on the price per gram display?

No price per gram is displayed, at least in the places I've been to.

I believe it's based on what the pack displays, if its grams then they show price per gram, if its ml, likewise.

I suppose its still possible to game with own label goods, from what I've observed it only seems to come up in a limited range of goods, sauces and suchlike.

I havent weighed a litre of oil, but a litre of water is a kg, so water based goods should be fairly comparable ml to g, that's the basis I work on anyway.

A lot of stores in Germany do something else, where they'll use the price per 100g for one brand and price per 1kg for another in order to make it just slightly harder to realize how expensive something is at a glance.

This is very true, common with e.g. cheese where the pricier cheeses are often per 100g. Still easy to compare but somewhat shady.

I have not seen that in France so I guess using the price per kilo or litre is mandatory.

Sometimes the average items have a price "per 1 kg", but the expensive ones have a price "per 100 g".

Yeah, you can easily multiply the number by 10, but it requires conscious attention.