It depends how badly you want to see something - and obviously if you have the money.
I paid £50 for our £18 play off final from a lad outside Wembley - I wanted to see it that badly and luckily had the money.
Similarly for the Oasis Maine Road gigs in 96, I was desperate to see Oasis, especially at Maine Road.
I think the tickets then were £18 too?? (I'll have to dig out my stub)
Anyway, it sold out extremely quickly and back in those days when the internet was in it's infancy (didn't really exist!!) there was an advert in the NME of an agency in London who had tickets.
So, rang them up and acquired two at £60 each - I wanted to see them that badly and luckily had the money.
So, relatively if someone pays £350 for a £100 ticket, it's rougly the same ratio that I paid all those years ago.
I would have paid £350 to see then at Heaton Park, guranteed........unfortunately this time I don't have the money!!