Last week I bought two half gallon containers of ice cream from Fosselman's freezer (Mocha Almond Fudge and Nutella). When I picked them up the the first thing that I noticed was how light they seemed.
Today I bought one quart of Trader Joe's Coffee Bean Blast Premium Ice Cream.
I could swear the one quart of Trader Joe's ice cream feels heavier than each of the half gallon containers I got from Fosselman's. I can't find my ktichen scale at the moment, but the one quart of TJ's is definitely heavier than the half gallon of the Fosselman's.
The half gallon of Fosselman's was like $6.30 and the quart of TJ's was $5.99.
Overrun is the amount of air that is incorporated into the product during the freezing process to increase the volume. It's expressed as a percentage. For example you have 1 gallon of mix and you end up with 1 1/2 gallons of finished product that's 50% overrun. Soft serve ice cream is normally 50%-60% overrun. The commercial stuff you buy in the grocery store is 100% overrun(half air, the legal limit). Super premium and premium ice creams will have higher butterfat content and lower overrun (15%-50%).