Just a fun fact, the amount of air churned into ice cream is called the overrun. In order to call it ice cream, the maximum overrun is 100%, or 50% air by volume and 50% milk, etc...
Another factor in ice cream quality is the emulsifier(s) and stabilizer(s) used (or not used).
Stabilizers and emulsifiers are not necessarily a sign of bad quality (especially since egg yolks are an emulsifier). Really you can find an inverse relationship between the number of ingredients and the cost of the ice cream. Stabilizers are used mainly to allow the ice cream to be transported, so it stabilizes the emulsion when the temperature increases (so you don't get chunky ice crystals when it refreezes).
If you look at a pint of Haagen Dazs, you'll see there are no stabilizers. They literally handle the entire supply chain to ensure that the ice cream stays frozen, and obviating any need for stabilizers. Pretty bad-ass, in a sense. Adds cost for little reason, in my opinion.