Want cheap mouse for $15?
Aula Killing the Soul.
I've been using it for 1+ years and it's working perfect , it's a chinise company though.
800 DPI to 2000 DPI.
Since you're using a MAC (why) you're probably gonna be playing on full resolution so you don't really need a 400 DPI mouse unless of course you're not playing on the native resolution.
The sensor is pretty decent , only problem so far is when you turn the mouse at 20012382190Km/h the sensor doesn't detect it , or I just raise the mouse in the air without noticing it.
Cheap and good ,working for 1+ years with lots of sweat.