Re: Mike Mechanic Business Practice???
I understand everything you are saying and agree with you (except you do actually have a defacto natural monopoly, which differs from a government sanctioned monopoly).
Most people that order from your site expect turnaround times to take a few weeks at most. Try giving them an idea how long it will take for you to produce the part that is ordered (tell them over the phone or put a disclaimer on the website), then send it out afterward. This will discourage people from complaining about long wait times.
Here's a good suggestion: charge extra for an expedited manufacture of a part and guarantee the shipping date. This way customers will have two options: be put in a pool of 1-3 weeks, or 3-day express manufacture (these are made-up examples).
Another suggestion is to try to find ways to make your business and production set-up more efficient and less labor intensive.