Collect the money before the presale if you can, or the same day you buy, into one visible place, not eight separate promises. The person holding eight tickets and seven IOUs has the worst seat in the house.
Presale opens, the group panics, and whoever has the fastest checkout buys for everyone. It's a heroic move that turns into a part-time job: the show is in October, the money conversation happens weekly until then, and one friend still "totally forgot" at the venue.
Concert math is rarely clean, service fees, the friend who wanted the pit while everyone else took the lawn, the presale that cost more than the general sale. Put the real number each person owes on their share, fees and seat difference included, so the buyer isn't quietly absorbing the Ticketmaster surcharge across eight people. Everyone chips in what their actual seat cost, not a rounded guess.
And when a friend backs out and someone new takes the spot, the record keeps it honest: the new person chips in, the original gets sent back what they put in, and the whole group sees the swap happen. Nobody has to remember who paid whom or whether the reseller ever squared up, the ticket followed the money, and the money's on the record.
The buyer holds the money directly, TableCash is the record the whole group sees, and cards are handled by Stripe, a licensed payment processor.
The worst move is buying the whole block of tickets on your card and then hoping four friends pay you back. Flip it. Everyone saves a card and promises their ticket money now, before you check out, with no charge yet.
The cards don't run until enough people are in to actually cover the tickets, then they all charge at once so you never front the block and nobody can flake after you've already bought. While the table is filling a person can take their spot back with no card touched, and it locks once it fills. That's the clean way to commit-now-pay-later on a ticket run.