I thought Crestron could not be purchased online.  If that is the case, did you bring it up to Crestron each time?  How big were these jobs?  I would not move forward with a client if they purchased everything on line on a big job without a very clear and concise contract in place that states we are not responsible for ANY issues on the job and all troubleshooting will be billable.  I also would be charging a much higher labor rate to compensate for the loss in revenue.  If they didn't understand this, I would walk from the job.