eBay still has the HTC One M8 available for just $489.99. This is the unlocked one, so it will work on AT&T and T-Mobile here in the US and most other carriers outside the US. The HTC One M8 features a 5-inch 1920x1080 resolution SuperLCD3 display, Qualcomm Snapdragon 800 processor, 2GB of RAM, 32GB of storage, and a microSD card slot. You can pick it up from the link down below.
HTC One M8 (unlocked) - $489.99