Interesting concept and I completely understand your value proposition to parents. Basically, don't get suckered into spending $300-$500 for camps and showcases that are designed to create a goodwill relationship with you as a means to get you to return to their next "pay to play" event. Baseball Factory is one of the first that comes to mind for me.
So your business model is that the parent will pay $xxx once to your service to come in and provide an "objective", no holds barred evaluation which the parent can then use to spend their money more wisely and not continue to throw good money after bad.
IF you can truly remain objective and not ultimately be driven by the market to begin telling parents what they want to hear so that you don't get bashed to the point that your service becomes poison, it makes sense. I do suspect that some level of objectivity would be lost as you would begin to protect a longer term business interest. I also believe that your service would ultimately never result in the goal you desire, which would be to prevent parents from "having" to spend money on multiple camps and showcases when their kid really isn't at the level they believe. I believe that the parents of a player who receives that "probably need to buy a pair of soccer shoes" evaluation from your service is going to simply chase another evaluation, camp or showcase until they get the answer they're seeking.
I get what you're trying to do, and I believe the market is there, but I don't think it will achieve what you hope and you may struggle to remain objective to sustain your long term business interest.