Do you pay your plumber full retail for a bathtub? How about that new truck? If you cut your clients a break (20% off retail, but only if you install) they feel you are treating them well and will refer their friends. If you charge them full list, they are going to be PO'd when they see it advertised elsewhere for less. But to each their own...some want to build a long-term client base, others want the quick buck. Off my soapbox.