I think the ticket has some kind of photo of the buyer on it - so if you were buying the ticket off eBay, you'd have to be buying someone who bears a vague resemblance to yourself. Even then though, £6million is ridiculous - someone must have made a mistake there.
EDIT: Wiki'd it;
"The 2007 festival will take place between June 22-24. As an extra
precaution against touts, purchasers had to pre-register, including
submission of a passport photo, during February,[20] before tickets went on sale on Sunday 1 April at 9am at £145 each. Standard tickets sold out in about one hour and 45 minutes,[21] with tickets for special coach and tipi deals selling out later."
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