Cafago offers this 7" 2-Din HD Bluetooth Car Radio for $63.99. Coupon code "ZK3836MG" cuts it to $43.97. With free shipping, that's $27 under the best we could find for a similar one sold elsewhere. It features MP5, USB, FM radio, Bluetooth 3.0, rear camera input, and an auxiliary input.
Note: it ships from China and may take one to three weeks to arrive.