I bought my 4" Pro-Comp SA lift for roughly $500 (in 2003), and it has performed for me in a variety of situations.
Jacume - Baja California
Huitzi's Rubicon runs a Rough Country 4" lift, and it cost him roughly $500 (in 2011)
1942 Pole Line Road - Baja California
When I have the $$$, I plan on upgrading. But, for now it gets the job done.