In reply to MarkJH:
> In principle, both pairs are taking up a single line at the wall whilst they are climbing, but if the belayer in the 2nd case was not paying, the wall would be getting only half the money whilst still seeing the same 'use'.
Not true, it's half the use, the cimbing pair spend half as long on that route, as the belayer doesn't climb. They then move on + spend half as long, as a pair, on the next route too.
They carry on doing this until the climber says.. Hey! This aint good, i'm only getting half/ none of my usual rest between climbs! Go have a cup of tea + i'll eat my power bar on the couch/ bean bag/ chill out zone.
I've done this, belaying only, explained i am injured but want to stay interested, eg, over winter, and not been charged, Redpoint Bristol, didn't charge, but whilst i popped into Gloucester Warehouse today, i noticed they have a 'belay only' charge of £1.50, which seems reasonable.
The thing is, there is little gain for the belayer, they are actually offering their services for free ( if true), and the climbing wall benefits if this was pre-arranged with the climber, by having a paying customer who may otherwise have not been able to climb that day, although perhaps they would have arranged something with a climbing climber for another day if no one (not even just a belayer) was available that day.