Is dropping out of a decent paying career to pursue a Ph.D in

Depends what your reasoning is and what your plans are. People do lots of things in life. You can go do an economics PhD, I can go sip cocktails on a beach for 6 months.

How do you drop out of a career? when you're done you just go back. That's kind of the idea of having a career, that you can just pick a job of your profession and get to it.

How much are you currently earning? <$100k? Because with a PhD level of economics knowledge you can easily make much more than that.

On the other hand you could just work your way up in finance studying economics on the side.