From my perspective (as someone who spent 2 years running a startup that tried to disrupt the diamond industry), I think the most difficult thing to do is to change the entrenched consumer sentiment. Without a shift in how they view these expensive purchases, there won't be disruption. This usually means spending tens or hundreds of millions of dollars on marketing the idea.

I've studied and analysed what we did wrong / why we failed to gain traction - and might try to attack the problems from a different angle if we decide to give it a second shot.