You forgot to disclose the rest of their reply!
"Given the time and resources required to diagnose this switch which in the end was not found to be faulty or a manufacturers defect, we will accomodate you this one time only by waving our usual $500 diagnostic fee.
As a courtesy, we therefore enclose an invoice for only $300 in addition to your $2000 upgrade charge.
Please note the limited warrantee associated with your upgrade is a generous 90 days.
Please allow at least 3 months for burn in before fulling appreciating the dramatic benefits of your upgrade."
"Given the time and resources required to diagnose this switch which in the end was not found to be faulty or a manufacturers defect, we will accomodate you this one time only by waving our usual $500 diagnostic fee.
As a courtesy, we therefore enclose an invoice for only $300 in addition to your $2000 upgrade charge.
Please note the limited warrantee associated with your upgrade is a generous 90 days.
Please allow at least 3 months for burn in before fulling appreciating the dramatic benefits of your upgrade."