So a couple of things. If he gets a 1.7 pop posted from a PG event, it becomes real. Until then, he has a time a dad says he has. So if you believe the 1.7 is legitimate, then you can legitimize it to the rest of the recruiting world by way of PG validation at a showcase.
To your original question, ShoveIt nails it. It's up to you. Know that not all PG showcases are equal in the amount of exposure that he will immediately receive. My son has done two, the PG Jr. National after his Sophomore year and the PG National this summer after his Jr. year. Absolutely no regrets as the attention and exposure he received has been phenomenal and worth every dollar spent (each of these were also $650). I would do both all over again, but to my point, both of these were their premier national events, probably only overshadowed by Jupiter which is really something between a tournament and a showcase in nature, where the Jr. National and National are pure showcase events.
At the other various PG showcases, you'll receive the same level of attention, coordination and management from the PG side, but you won't have as many scouts in actual attendance as you will at the previous events I've mentioned. The write-up and database information will be the same, so what becomes available to their subscribing scout base will be legitimate there for your son. It will also give him a true opportunity to see where his metrics stack up against his peers. One thing that you can say for PG, most of the top 100 players in each class have PG recorded metrics posted for all to see. Not too many other showcases can boast that. So while you may believe your son has the best pop time in the country (or pitching velocity, or exit speed or 60 time, et al), you will know for certain if you get it logged and posted via a PG showcase.
It can open doors, but no guarantee that it will. Remember, PG is an amateur scouting bureau. Make no doubt, the guys evaluating at their events are scouts. If they are impressed by your performance it will be communicated to decision makers at the professional and college level.
As ShoveIt basically states, attending their event doesn't make the player. It provides the stage. It's up to the player to perform. If he does, it can be worth every penny. If he doesn't, you've got an expensive hat and jersey for the effort and a realistic snapshot of where your son stacks up.
edit after reading JoeMktg's post. Completely agree with him. Whether his strategy for attending the showcase is to get unbiased metrics or in front of specific coaches, you need an overall recruiting plan to execute. Unless the plan is to showcase and have colleges tripping over themselves to get to your son (in which case he's a stud and you already know that), develop a solid plan of which a PG or local showcase may or may not be a part.