I don't believe that a person needs to take in 500-700 grams of protein a day to build a decent physique.Also don't believe in the eat every 2-3 hrs rule of thumb neither.As a 16 yr old I built a decent body w/just mom's regular 3 squares a day plus snacks.You do need protein & have to eat but it also depends on how many calories per day you are expending also.A person that simply trains while another that trains but is also involved in other sports will need more protein (overall calories actually).I myself like to eat only when I feel hungry, average probably every 4hrs.I feel that as long as you eat your meals but "snack" in between them & make sure protein is a part of all meals you eat you will make gains.By snacks I don't mean a bag of Hostess chips either but let's say a simple chicken sandwich w/maybe a glass of skim milk.Saying this, the pros if true how they eat must keep a plunger next to their toilets always at the ready!
That's as a 16-year old. Keep in mind that you don't start out eating that much; it's a gradual thing. The pros about whom you read that consume that much protein have done so over a space of time. A teenager will likely do well with about 200 grams of protein, unless he's a twig with a flame-thrower metabolism. In such a a case, he may need 300 grams of protein (maybe more) to get bigger.
I've gone as high as 500 grams of protein for a brief period of time. But, that was a gradual progression. I ate 350 grams for several months. When I stalled, I bumped it up to 375 grams and stayed with it, until that stalled, and so on. As for the pros, they don't have "decent" physiques; they have massive ones, which requires FAR more nutrients.