Are early-bird discounts ribbis? For example, "buy before March 1, 10% off", or "tickets $12 in advance, $15 at the door"
Inspired by http://myparnasa.com/collecting-interest-ribbis/
I'm the writer who wrote post about Ribbis cited here.
I've since read the Artscroll book about Ribbis by Rabbi Reisman, and he says that Early-Bird discounts are usually considered Ribbis. Since it's d'rabbanan ribbis, there may be leniencies (e.g. for non-profits, corporations) but it's pretty complicated.
If you are planning to do an early bird discount or any other pricing strategy to gets people to pay sooner rather than later, read the book or ask a shayla. Kol tuv and thanks for posting