For example you mention cars. The almost identical VW Golf (know as a Rabbit in the US) cost more than twice as much in Denmark as in the US.
http://www.numbeo.com/cost-of-living/compare_countries_resul...
Yes, but the VW Golf is relevant in the U.S., and irrelevant in Denmark. In the U.S. you have to drive, and in Denmark you don't (and most people don't). The modal share of bicycle commuting in Copenhagen is >50%, because the bike infrastructure is good. I sold my car when I moved from the SF Bay Area to Copenhagen, and now I spend less on transportation, with a better quality of commute (in my subjective estimation). Yet PPP would probably claim transportation costs more! Besides the nice bike infrastructure, I have an unlimited-rides metro pass for $50/mo, which includes very good 24/7 service. How much would it cost me to buy 24/7 transportation in the SF Bay Area, where I don't have to drive the vehicle myself? (Night buses that come once an hour don't count.)
I would rather work for 10 months in NY and live in Maui for 2months vacation than spend $15000 traveling to Maui five times for a week each, but GDP says the latter is a higher standard of living.
Sort of like your doctor wanting to know your blood pressure for somethings and your weight for others. They can both tell say something about your risk of heart attack but blood pressure also indicates other more immediate issues and your weight is vital when prescribing medication.
EX: Subtracting exports and adding imports is useful when tracking quality of life adding exports and subtracting imports is useful when measuring economic strength. However, the difference between exports and imports tends to make up a small fraction of the economy so it's not that important.