If you have a Fry's electronics nearby(or some other store that price matches internet deals), and a smartphone that can bardcode scan:
Go to the store,
find the mouse you want,
scan the barcode,
if you have a droid use google shopper to show you the lowest price,
profit.
See, I filled in that ???? bullshit for you.
Thats how I got 50 bucks off my newest mouse AND was able to find one that fit my hands right.