What actually is your complaint there?
That they bother having a (spectacularly good value) U-10 price, rather than charging ALL 'kids' the same?
That the club counts U17/U18s still as kids, rather than only U16 like many places?
There should be a further differentiated price for 11-16 or 11-14 yrs which more reasonably bridging the gap. To charge a child that is required to be accompanied the same as those over 16 is taking the proverbial.