Interesting that the mouse is considered as something as "up to $70". After you get used to high-dpi gaming mouse you can't even work properly with <$100 models.
Just like moving to SSD felt like a revolution, for me moving up to a gaming grade mouse has been.. irreplaceable.
The precision and speed for any mouse-oriented task saves quite some time and especially gives a great feeling of having better contact with the screen. Highly reccommended.
It takes a few days to get used to moving your hand a lot less than before but think how much less strain!
Current setup: Logitech G9X and Razer exactmat. Previous mouse was Razer Lachesis but ergonomically it was somewhat crap.