Historically, food was bought by mass; balance scales compare masses in the same gravitational field. The difference between mass and weight was entirely irrelevant until the concept of gravity was noted. It's only with the advent of spring balances that you actually measure the weight of something to determine its mass.
If we colonise, say, the moon and have such mundanities as grocery stores, they'll sell by mass since the nutritional content of the food doesn't change with the gravitational field it's sold in. Likewise, 'weightless' food in freefall.
If we colonise, say, the moon and have such mundanities as grocery stores, they'll sell by mass since the nutritional content of the food doesn't change with the gravitational field it's sold in. Likewise, 'weightless' food in freefall.