Costly incorrect assessment of repair requirement

I have used Bergen's services in the past and found them satisfactory, if perhaps a tad expensive. So when my Bosch dishwasher broke down this week, I contacted them again. They sent a truck to collect my machine and to assess the repair requirements.

I was informed that the electronic control board was faulty and would have to replaced, at a cost of over R4,000. Since this was unaffordable, and for not much more I could buy a brand-new machine, I declined the repair and retrieved my machine. And just to be sure, I called in the services of another company for an on-site assessment and repair.

This company sent its technicians around, who opened up the machine and ran some tests. The outcome was that a pressure sensor valve was faulty and needed replacement. This was done at a total cost - callout, part replacement etc - of R1,480, and the machine now works perfectly again, at a considerable saving.

I do not understand how or why Bergen's apparently made such an error.