Damn - lost my post.
Anyone can do the job 85% correct. It takes a true professional to give his clients 100% of what they are paying for. ie. technically correct install, neat and professional looking install and a jobsight left as clean as when the installers arrived and educating the client before and AFTER the sale. These are the qualities that make clients come back for more and tell their friends to hire you even if your are more money. Don't cut corners to cut the cost. Make your customers pay for the final 15% of the job. They'll appreciate it in the long run and your business will too.