The Havaianas pop-up shop (in front of Puma) has pairs starting at $10. When visiting today they also had buy 1 get 1 free so we paid $10 total for two pairs. Size choices were fairly good.
Not sure if this applies to all models or only some.
[Edit] According to comment below the buy 1 get 1 is only on the 10$ range.
Buy now, sell in summer :p