If something's so expensive you can't touch it, it's prohibitive. That Ferrari in the showroom? You may want it, but its price is prohibitive.
Prohibitive originally referred to something (often a law) that prohibits or forbids something, but came to mean conditions (often prices or taxes) so high or great they restrict or prevent something: "To some, the cost of child care is prohibitive." The stress is on the second syllable, just like the verb: pro-HIB-itive. If it's a matter of expense, a synonym is exorbitant.