In reply to Jon Stewart:
> (In reply to James Oswald)
>
> One could also argue that economists should pay a small fee every time they introduce a free-market argument where they are well and truly not wanted.
Haha! This isn't really a "free market" argument. The free market exists here, people have chosen to go to the crag, instructors have chosen to instruct. But, when they do so they harm others (queueing, congestion, polish etc). This is a cost to a third party, one other than themselves which they don't account for when deciding to go to the crag. Small charges for going to crags that are busy would encourage people to go to other crags, ones which are quiet.
It's the same argument as to why congestion charges are desirable during peak times, lots of people choose to drive at a specific times of day (rush hour) and the result is that everyone waits. It's a collective action problem. The people who value going to these crags the most can use them, others can choose to go elsewhere.
I'm not advocating a "free market solution". I'm advocating intervention in a "free market" that isn't performing well.
P.s. In practice, I realise it might be completely infeasible.