My son also received the above mentioned invitation yesterday. I had the same skeptical reaction when I saw the price associated so I called a local Area Scout that I know pretty well.
His comment was that it is NOT NECESSARY. This is strictly a money making showcase and it will only be scouted by Area Scouts and SOME local colleges. Come draft time, it will play NO part in what decision the higher ups in a pro organization decide. As for the college guys, PG puts on several tournaments throughout the year that are scouted very heavily by both college and pro guys, and are much cheaper (Jupiter, WWBA tournament, etc.).