But it is! It's just cross-selling.
When you sell a guy a suit, you don't offer the belt first, you go for the money item, the suit. Then after he buys the suit you sell the belt because its less of a big deal since he's already spent the money.
With that in mind, how much is super sizing in relation to the original meal?
More like relative cost- the price of the belt is a small % of the price of the suit as a whole. Similar to how it's easy to sell the power seats, w/e other luxury on a car for $200 when the car is $20k+.
Anchoring would be if the suit salesman shows you a $3k suit to start out. Or more realistically say an $800 suit for your average person-not so outrageous as to offend you, but probably still out of your range, so you'll be more likely to spend $400 on a suit than if he had just started out in a more standard $300 range.
With that in mind, how much is super sizing in relation to the original meal?