If you spend 10k hours perfecting something no one else even thought of trying, chances are you'll be the best in the world at it.
So... like get a PhD?
And many outside that too. From medieval weaponry to chicken shop reviews, the internet has a fair people who make a living off all kinds of very specific subjects that most people wouldn't even think about.
Because generally, no competition means no demand, so while it might be satisfying to be best in the world at something, an obscure skill might not translate into financial success.
Since the field is currently successfully employing a million people there must be that many profitable pieces if you slice it correctly.
To make this example even more specific, maybe you are good at writing fast decoding algorithms for new telecom standards.
There is also a lot of now low-hanging fruit in compressed sensing for the mathletes/computer people who know what that's about.
Edit: Actually, just learn math if you're looking to get ahead and have an advantage over many people. This advice doesn't make for the best blogpost or YouTube video but it's effective.