It'a all subjective. People who have 4-zone CC, will tell you that you can't live without it. People who don't have this option will tell you to save money.
I don't have it, and in HOT California weather and black leather interior, the back gets cooled down quickly enough, so I think you should be able to save 2K
2011 528i Space Gray Metallic / Black Dakota Leather / Dark Wood Trim / Prem Pack / Nav / PDC / USB-iPod