Don't be fooled by what may seem like a cheap price. That one angle grinder that is $30 can be purchased at Harbor Freight for $20. They even have a cheaper one for $15.
http://www.harborfreight.com/catalogsearch/result?q=angle%20grinder
I have both of those grinders, and they both work find and I have been using them for years, but honestly, the Ryobi angle grinder that I have that was about $65 is head and shoulders superior to the cheap ones I have. I have 4 angle grinders. One with a 6" wire wheel, cutting disk, grinding disk, and flap disk sanding disk. I do a lot of metal work, so having multiple angle grinders makes it quicker that changing disks all the time. I just grab a different tool.