I don’t see why there needs to be a cutoff? In my country we list exact prices and weights. Of course there’s room for error with the actual weight of the product in some cases, but that’s unrelated to the label itself.

Listed is how many pieces, total price, as well as price per piece.

Same with weight, though gram instead of piece, as well as price per kilo, making any sort of conversion easy.

And same thing with volume.