Currently around $3.10 at time of posting for Beat The Average. Personally I don't think top tier is worth it but certainly the BTA isAs below
Pay what you want!
The Warlock of Firetop Mountain
Hand of Fate
Pay more than the average of $3.04 (about £2.29) to also unlock! (at time of posting)
Hacknet Labyrinths (DLC)
Pay $12 (about £9.02) or more to also unlock!