I was reminded of an excellent example of this today at the pharmacy, when I was shopping for medication for a cold I am currently fighting.
My favorite cold medicine recently released an extra strength version. I studied both of the boxes carefully; I had to anyway because I have celiac disease and reading ingredient lists is what us celiacs do. Anyhow, it appears that the only difference between the regular and extra strength versions is that the regular version the pills have 200mg of the active ingredient and you take them three times a day, whereas in the extra strength version the pills have 300mg of the active ingredient and you take them twice a day. So either way you're getting 600mg of the dose each day times the number of pills you take at each sitting.
The regular strength box had 18 pills, the extra strength box had 12 pills. So in both cases, you are paying for 3600mg of the active ingredient. Other than the instructions on when to take the pills, the two bottles seem identical in every way.
Except for price. The regular version costs $9.99. The extra strength version? $15.99. By introducing the extra strength version the company was able to charge more for an identical product, to people with more money who do not read boxes too carefully. Of course, the downside is that it (arguably) weakens the brand perception of the regular strength version.
One thought did occur to me - even though the two products are identical (or at least appear to be), I wonder if the extra strength version would do better in clinical testing that regular strength version, if both groups were told in advance which version they were receiving. I suspect they would, due to the placebo effect. So maybe the two bottles are not so identical after all.