Tickets are now reduced by twenty percent.
Explanation: The joke plays on the fact that One Direction had five members, and if Liam Payne (one of the members) had died, there would now only be four members left. A “reduction by twenty percent” humorously refers to the loss of one-fifth of the band, or 20%, implying the ticket price is reduced to reflect the missing member. It’s a dark humor joke, leveraging the math behind the reduction and the band’s member count.