Incredibly common in the US as well to use different units per item. All the better because our garbage measuring system can make unit switches significantly trickier.
I had to do a double take a few weeks ago when I found the price/unit to be drastically different for the name brand to the store brand of something, until I realized they strategically switched the <unit> (# to oz I think it was) to make the store brand look astronomically cheaper instead of just slightly cheaper.