We charge our normal hourly rate, and prices with good margin for wire + materials. We rarely do builder spec homes, so most rough ins are part of a much larger contract. We generally throw a +/- 20% estimate to the builders, then bill them actual T+M after we are finished with each phase. If they want a concrete figure, we figure it out based on the plans, conservatively estimated wire lengths, add labor, then pad it to cover our rears.