Amazon’s Deal of the Day is on Magformers. You can get up to 60% off while supplies last on 18 different sets. For example, you can get this Magformers Inspire Set with 100 pieces for $77.99 (reg. $219.99).
There are some pretty good deals (I try to find these for under $1 per piece…although some of the specialty sets are a little more), but please remember that prices may change.