Re:Snickers King Size
Yep, the response I got from Mars was the change was due to price.
"In response to your email regarding SNICKERS BRAND.We appreciate your comments and assure you it is the policy of Mars Snackfood US to offer the best possible consumer value at all times. Our wholesale prices are commensurate with the costs of all raw materials as well as the many other business costs. For example, today's prices of cocoa, the basic ingredient for chocolate, are extremely high. The size of the product was changed in order to hold the retail price steady. This is also directly related to manufacturing and ingredient costs. When you compare the weight of any product of equally high quality, we are confident our candy would cost less per ounce."
So the move was made to avoid a price hike. I don't know how much of this decision was also to streamline the american version with the british version.