ebecker's formula is good but wouldn't work here in Washington. Builders are too used to getting the shit given to them. As competition increases (if it hasn't already) where you are, you may find prices like $90.00 for a full room of speakers and VC (pre-wire... not trim) and about $80.00 for the full drop of 2RG6 and 2 C5. You'll also find panels and modules being sold for about $2.00 more than they can be bought at your local AVAD. We've talked till we're blue in the face but most builders only care about getting the house sold. Most of the electricians doing the work around here cram all of the wires into the tiniest enclosure they can get and wirenut the phones together, eschewing the modules. You need to check out your market, find out what you do better and determine whether the current going rate + what you can get a builder to buy into as extra and worth it, can sustain your business.