There are only a limited amount of tickets, and loads of people want them (think all the Ed Sheeran fans) when the tickets sell out, there are even more people who want one per ticket available, so whoever’s selling it can ask for more. At it's simplest level, it's just basic supply and demand. This is what one Ed fan had to say about it:
disgusting! If everyone refused to buy them then they wouldn't do it, it's the laws of supply and demand!
The ticket resale market technically exists so that fans can innocently resell tickets for gigs they can no longer go to. The problem here is that it is being used by professionals to buy up huge numbers of tickets and sell them on.
The Observer did an investigation into the issue and found that some touts had established businesses worth hundreds of thousands of pounds, based on reselling tickets. One tout they spoke to said he got round the rules to stop people buying loads of tickets by using lots of different identities and credit cards. While others are thought to be using technology – bots – to buy up tickets as soon as they go on sale.
Basically, the problem is that while reselling is legal, for it to be happening on the scale it is someone must be bending the rules.
Some places have brought in laws to combat it. Queensland in Australia has a law that stops people reselling tickets for more than 10% more than their face value. So Adele’s $106 ticket wouldn’t have been able to be sold for more than $116.60, way short of what some were actually going for. There are calls for this 10% cap to be adopted around the world.
Some economists argue though that too much of this kind of on markets like this actually harms the economy. Sajid Javid, who used to be the culture secretary for the UK government once said that touts are filling a gap in the market, and said they were just "classic entrepreneurs".
The economist who wrote the UK Government’s review said that he wouldn’t advise any more legislation as it would only push the market “underground or offshore” – which would basically make it even worse. He also said a price cap – like the 10% cap in Queensland – would be too hard to manage.
A few “ethical” resale companies have popped up to try and combat the problem and make the most of the wave of public resentment against resale companies. Both Adele and Ed Sheeran have publicly partnered with one, which lets fans sell unwanted tickets, but never for any more than the original sale price.
Ticket reselling is legal in most US states and most of the rest of the world. The main arguments against it are ethical. If prices for major shows like Ed's or Adele's continue to rise, soon pretty much all fans will be priced out, which is why Ed's so angry.