Best Buy offers the Logitech Wireless Performance Mouse MX, model no. 910-001105, for $49.99 with free shipping. That's the lowest total price we could find by $20, although we saw it for $5 less in December. It features four thumb buttons, scroll wheel, and Logitech unifying receiver dongle that allows the addition of a compatible wireless keyboard without multiple USB receivers.
From shoes to cookware, if you're willing to pay a little more for these awesome products, you may never have to shop for another again.