I have from time too time had spare tickets to sell, and had never considered that the person buying them is then going to sell them on again for huge profit.
If you look on e.bay, numbered houx tickets are selling there for £100+, the same guy has 5 I think at the moment for sale.
The camping ticket situation is getting out of hand now, less than 10 years ago we never bothered pre booking, Now I am sure people are pre booking far more than they need and selling them on for huge profits.
In my view, the ACO are aware if this and see the large mark up and will over time hike the price to match.
Maybe the ACO should stop selling camping tickets in advance and just sell them on the gate?