Cheapest it's been according to CamelCamelCamel (43.24GBP)
MX Anywhere 2
From office to external meeting to business trip to home and back to the office, Logitech MX Anywhere 2 works anywhere and everywhere you work, including on glass. Crafted to fit your hand, it provides the comfort and control you expect from a wireless mouse. You can connect to Windows and Mac via the small Pico Unifying receiver (included) or via Bluetooth Smart wireless technology. Pair this mouse with up to three devices and easily switch between them with the touch of the button, thanks to Easy-Switch technology.