The HTC-made T-Mobile myTouch 4G was originally priced at $149.99 for new users signing up for a contract and $450 off-contract. Then in early November 2010, the price dropped to $79.99. Today until 5/5/11 (i.e. tomorrow), the mid-range Android device is completely free on T-Mobile with a 2-year contract after a $250 "instant discount" and $199.99 "web-only discount".
Strangely, the refurbished models are still priced at $49.99. Someone at T-Mobile must have neglected to change their prices!