Pretty sure we only spent only 10's of $K, not $500K, to have MET Labs perform certification of a product. But to keep life simple, we did not enable Bluetooth (no intentional radiator, so self-certify rather than lab certify to FCC standards.) And, we used a listed 100V ... 250V to 24V 240W adapter, avoiding all lines voltage issues.
Met Labs is an NRTL.
When it comes to UL Listing, is that something only UL themselves can do? Or can any NRTL perform the testing, and results are recorded at UL (if that is where the listing has to be?)
I wouldn't think there would be a monopoly on the process of UL-1741-SA.