I would bet that MS has nearly as much revenue as a company like Logitech, when it comes to peripherals.
Although, to support Squills post, I did purchase a Bluetooth Logitech mouse today, for my laptop, over a MS one. The MS one looked crampy, and was an ugly color to boot. ;)
The retailer had a good mouse selection from both companies, however. Frankly, you just can't find a retailer that doesn't carry MS keyboards and mice. I sincerely doubt they are struggling with those items, since they are sold at monstrous margins.