I paid £3 for the weekend ticket to the Isle of Wight festival in 1970.
Ok back then it was half of my week's wages and you could get 8 pints of larger and lime in a pub for £1: but Hendrix, The Who, The Doors, Free, Taste, Chicago, Family, Joni Mitchell, the Groundhogs, ELP, Miles Davis, Ten Years After, Melanie, Sly and the Family Stone, Jethro Tull, The Moody Blues, Richie Havens, Joan Baez, Leonard Cohen and loads more for £3!
One thing about being an old codger, you certainly got the opportunity to see some class acts when you were younger!
Edited to do a sum: if the average uk price for a pint is now £3 and you could get 8 pints to the pound in 1970, that means a £3 weekend ticket in 1970 would cost you the equivalent of 24 pints x £3 today, which is £72. To put that in perspective, the ticket I bought to see The Who on Thursday, including booking fees cost £78.