Basic economics - you pay people for their time
"And anyhow, how can you put a "value" on a concert?"
By selling tickets for it, perhaps?
"If a person (or band) wishes to sell their services at some notional rate to a perceived group of buyers (the audience) and determine that they are happy with £X/hour, then that is their right to do so. The fact that "the market" values their time at something much higher is only relevant if they are interested in maximising their revenue for this particular event."
Supply and demand is not just about maximising revenue, it's also about making the right number of products (in this case, tickets). Led Zep could satisfy any number of show goers at £5 per ticket if they were willing to play an infinite number of shows. If they care about the 'right people' seeing the show, then why don't they just do that? Or maybe even put on a freebie in the park?
"Basically what Led Zepplin is saying is, we're shafting you with the ticket price already and we don't want anyone else to think they can shaft you too, thats our job and our job only."
Quite. It seems to be standard record company ecomoronics - we can't be bothered to exploit this product properly (either for the musicians OR the public) but woe betide anyone else who tries to work around our broken business model. Is this the same reason why if I want a Stevie Wonder tune to listen to I can't just point my browser at motown.com, enter my CC number and download a lovely, 24bit, 192Khz audio file of it? OK, they have a piss-poor discography outdone by just about ANY fan site or site like allmusic.com and a craptacular link to iTunes, but is that really the way to exploit one of the most talented and prolific musicians of out time?
I used to think that the 'music' business was evil, now I realise they're just incredibly lazy.