Well, there's nothing cheap about the trackballs, but they're worth it.
If we're going to allow $30 mice, then my $29.99 Fry's sale 3500 DPI Razer DeathAdder is my favorite
cheap mouse. Very comfy, no signs of wear despite being near a year old, better tracking than my optical trackball, two extra buttons, doesn't require lift - even though it has very little room to roam, and its black and blue like my rig. I don't use a mouse pad with it and until I get an L-Trac, its my primary mouse at home.
My former mouse, a cheap optical ($10<$15) is still working over a decade now. It is on loan to my sister, who for reasons I don't understand would rather use my ugly cheap-O, than stick a piece of paper or get a pad to put under her more picky mouse. I got it at either one of the Office stores or a compusa from a mid aisle bin full of its siblings. It is so generic, neither did its packing, nor it proclaim branding or a manufacturing company of any kind. The only thing I know is its serial number and it was made in China. Its main flaws are it wasn't really meant for the 1600 and up resolutions, its surface is a little too slick now and the mouse buttons can stick up during use, so that you have to take a moment to pop them back down. Otherwise its a good durable cheap mouse with 3 buttons, one of which is the scroll wheel. Here's some crappy pix of it:


It is not as shiny as it looks in the pictures. Also, its red, not pink. .