This reminds me of the thread about using heating oil (kerosene) instead of Jet-A1. Chemically identical, but one is subject to much higher quality control processes and more stringent checks that maximise safety.
I imagine the main benefit of a certified component is that its provenance has been authenticated. A non-certified part may have a dubious provenance that could ultimately manifest itself in a catastrophic failure. I appreciate that the AAIB believed it found nothing on Mark's Gazelle that had a material effect on its airworthiness, however, there wasn't a lot left of the aircraft to check and there are several people who can recall stories of Mark's cavalier 'that'll be alright' attitude to his flying. The reality of this situation, is that although illegal, the aircraft was probably safe and it was the pilot's decision making process and attitude that was unsafe. Even though Mark was popular as a lively maverick, it was this attitude to 'the system' and common sense that lost him his life.
Stringfellow:
The mine mark ran existed right on the line of economic viability and making it pay meant not necessarily cutting corners but constantly asking 'do i really need this....??' We all talk about this qualification and that qualification but mark had no formal qualification in business yet became a millionaire.
I don't believe the mine was barely viable; as you said in the same sentence, it made him a millionaire. He could have afforded the certified 'legal' components if he'd wanted to.