If i buy tickets from a scalper on the day of an event, how much more should i expect to pay?

Answer 1

depends on the event, location of the seats
a few years ago I bought 2 tickets for Jethro Tull middle front row and paid 4x what they were originally selling for

Answer 2

I would probably say not much more than the tickets are worth. The scalper should be in desperate need to sell the tickets cause if he doesn't it will be his loss, so you can use that to your advantage and deal with him a 'lil.