alt Hacker NewsIDK man - this is sort of true, but I think you under-estimate how quality and price scale. A Jumbo-Choco-Monaka at 7/11 is still a fantastic value at ¥160 even if you adjust for purchasing power. GDP Per Capita (PPP) is about $85K in the US and about $60K in Japan, but even granting a 2x increase for California then a $2 choco-monaka would be a steal. As it is, I just spent $4.50 for an Its-It about an hour ago and while I am quite a dedicated fan of these things I would have gladly forked over ¥700 for a Chocomonaka if such things existed in California. I realize that people don't live out of 7/11 for their daily groceries and your point has some validity, but the quality/cost is still a great deal relative to what you would get in America.
$85K vs $60K ...to give you some idea the typical wage in Okinawa for a combini job is about $6/hour. I think the income disparity is larger than those numbers suggest.
FWIW Japanese people living there tell me combinis are expensive based on their salaries and I believe them.