I've been in the US for almost 15 years and it ain't all its cracked up to be as far as the earning power for merchandise, if anything, the margin of your comparison leaves out a ton such as those Perf mentioned. But if you live wisely within your means, sure, it works out pretty well but not by very much. Sure, you earn in dollars which seems a lot in Php terms, however, you really have to factor in paying to survive in a country that costs a lot of get around, costs a lot to be part of the system (taxes...taxes...taxes), and costs even more to break even and retire comfortably because SS doesn't even cover much unless you were earning a lot during your working years and shovelling money into a CD or foundation fund.
Afterall, unless you main job IS music, you really don't work solely to feed your GAS habit, and even full fledged musicians I know don't buy THAT much gear. They earn more money to eat better on tour because rest stop food doesn't exactly count towards guaranteeing a better bill of health when you are on tour for 3-6 months. So, point is that people have to eat and factoring your teller salary solely for a guitar is, well, weird unless you happen to want an edible guitar:) People work for other things bigger and more essential than GAS. At least I do. I may have dabbled in music for years and sidelined in it but it isn't my main profession because, lets face it, the US is competitive enough for musicians to actually "make it" here. One needs something more permanent to put food on the table.