MyTechSolution via eBay offers the refurbished Logitech Performance Mouse MX, model no. 910-001105, for $44.95 with free shipping. (NetDirectSales via eBay charges a few cents more.) That's $3 under our mention of a refurb from October and the lowest total price we could find today by $3. (For further comparison, we saw a new unit for $5 more in April.) It features four thumb buttons, Darkfield laser tracking, Logitech unifying receiver dongle, and more.

Of note, no warranty information is provided.