If the ground is a commercial operation would imagine the fee is what one would expect
50 carts & clays - £30 ish which is what one spends on average for practice regardless which leaves £28 for what will be an hour for the “professional instructor” plus the few extra over costs that this type of intriduction / instruction offers, theres not a big fat profit on this.
If you have some but very little experience of clay shooting, do converse with the ground / instructor, a tailored to your needs session such as this may well be of more value in the long run (and some like me are on a very long sometimes pained journey) than the £58 cost.