I posted earlier on this thread, but your insightful reply, especially about your OVP problem, prompted me to reply again.
Our computer repair shop has the same policy.
In addition to not charging the customer for our on-the-job education, we also do not charge for the time it takes to locate the myriad of computer and laser parts, especially nowadays where we have the internet and are fortunate to be located where we can use a cable modem.
Our markup rate is 30%, no exceptions, except when bidding for contracts, where it is dog-eat-dog, and let the lowest bidder win, then figure out how to stay in business!
Many folks would be surprised to discover 100-250% markups between wholesale and retail, which in a pure retail environment is often eaten up by exorbitant rent (location, location, location).
Computers and parts defy the norm, where prices continue to drop. For instance, in 1996 I built my first Pentium PC, 100mhz.
I was beginning to dabble in graphics, which requires large amounts of memory. I purchased 64mb for an exorbitant $2000. Nowadays, the same memory costs $49. But I digress.
Regardless, it will be interesting to see the response, or lack thereof, that the revelation of your experience triggers with the shop owners here.