The sad state of the economy (bailouts! Ponzi schemes!!) might be precluding any big-ticket purchases right now (put that Bentley on ice for the time being), but luxurious spa treatments can be (make that SHOULD be) necessary indulgences -- especially in these trying times. Many Chicago spas are upping their game with deluxe treatments, adding everything from champagne and caviar to 24-karat gold and gemstones to facials, massages and body services. Note to self: This is not your ordinary mani-pedi.