Interesting question. I was thinking about posting something similar.
I went to Safeway last week and bought 2 jars of Maxwell House instant decaf coffee. The first thing I noticed is that the jars are now plastic (I bought coffee earlier this year and the jars were glass). The second was the obvious size change.
I had finished the last glass jar of coffee I had the day before. I had not yet thrown it away. When I got the jar home I poured one of the plastic ones into the empty glass jar. The volume was 3/4 of the amount compared to the glass jar. And the price was about $2.00 more.
Changing volumes and often keeping the same size packaging is a valid, but sneaky way of increasing the price of a product.
Manufacturing companies realize that people don't want to "see" an increase in price, so they go about it in a non visual way. Same packaging, same price, but a lesser quantity in the bottle/box. Most people aren't aware that they are getting less for their dollar than they did before because most people just look at the package and price and take it for granted that everything is the same as it was the last time they purchased.
The worse case of this that I've seen is from Adrian Arpel, a cosmetic company.
I had a facial there once and purchased some of their products, including a great smelling facial toner. The spray bottle was the
visual size of a regular standard sized bottle of shampoo. I paid twenty-some dollars for it. This was back in the 1980's. Twenty-something dollars was a lot of money!
However, a few weeks later I discovered that the bulk of the plastic bottle was actually hollow, and that it concealed a metal spray can inside that was only about 2 inches deep and contained about maybe 1/4 of the amount that the plastic bottle visually appeared to hold. The volume of toner was 60 ml (1/4 cup or 2 ounces). The bottle that contained the metal canister, would have held about 250 ml (about 1 cup or 8 ounces) if it were filled with liquid.
Was I every ticked off! I complained to the company, but their response was that they had the actual volume of product listed on the bottle and I should have known that the volume was less than the size of the bottle it was sold in. Like DUH!!!!
I never bought from them again.