i use a rack about 90% of the time. I sell it as a labor saver. I typicallyu explain in my "Job Scope Summary" that the rack saves labor, enhances cooling and offers ease of future upgrades and servicing. When/if they ask to save the dough of the rack, I typically add back at least half of the cost to my labor at which point it almost always goes back in. If its a tough job, I'll bill for the labor and add the rack for free but skip trim strips, custom shelves, etc.