This was a better idea than simply saying a single use package really contains more than one serving in it to look like the company was being responsible.
You choosing to eat more is just that, your choice. It has nothing to do with any company.
I'm not sold the magnitude of the effect is really worth much though.
The same thing has been said about pints of ice cream. They are (or were?) labeled as being 2.5 servings - reasonable - but lots of people just ate them whole and then complained that they had too many calories.
Let's say Mars sells the bars to distributors for 20 cents and it costs 10 cents a bar to make and package.
A pound of milk chocolate costs $5 and you can get 250 bars out of it. Meaning, every bar has 2 cents of chocolate.
Chocolate prices go up to $6/pound. Now, every bar has 2.4 cents of chocolate. You can maybe eat that cost. Depending on the price increase of other ingredients. Eventually, chocolate hits $10/lb and you are spending 4 cents per bar on chocolate.
You can increase your price, OR you can use less chocolate per bar. You can slightly shrink the dimensions of every bar and use a thinner layer of chocolate to get your costs back in line with 2 cents per bar.
Everyone is going to notice your prices increasing. Fewer people are going to notice your sizes decreasing.
Always remember: if McDonalds could legally and without risk of negative PR: _double_ the average customer spend at the cost of _halving_ their life expectancy - this would bring the same revenue in half the time which would be a great corporate decision.
These people see a normal healthy person as an underutilised resource. The fact that a person could be a healthy weight means they have not consumed enough product. These people are pure scum and the only worse parasites on earth are in private equity on Wall Street.