[fee] = [PayIt2 fee] + [payment processor fee]
f = $1.29 + (2.9%*[ticket price] + $0.30)
f = $1.29 + 0.029t + $0.30

Profit, or the amount of money that finally gets to the organizer, is calculated based on:

[profit] = [ticket price] - [fee]
p = t - (0.029t + $1.29 + $0.30)
p = t - 0.029t - $1.59
p = 0.971t - $1.59

When the organizer opts to pays the fee, they're setting the ticket price and opting to get the profit left after the fee, which is simply found by the above equation. When the organizer opts to pass the fee to the buyer, they're setting the amount of money per item they want to receive. Therefore, to calculate the appropriate ticket price, we solve the above question for t:

p = 0.971t - $1.59
p + $1.59 = 0.971t
(p + $1.59)/0.971 = t

Therefore, the above equation is used to set the ticket price the ultimately pays to cover the fees.