How to silence the voice that tells you you're being financially irresponsible by spending 4 to 6 years doing a PhD? I'm very conflicted regarding applying to (American) PhD programs vs. not doing so and finding a job in industry to have more money.

The thought of doing a PhD makes me feel financially irresponsible; yet, I have concrete research interests and would be doing a PhD for the right reasons.  I've also been told that my application would be strong for some good schools, so I feel I'd waste a valuable opportunity.

How do you decide to do a PhD, knowing that it's the "poor" route to take for the next 4 to 6 years of your life?  It feels like a reckless move, but at the same time, a dream worth pursuing, and that nothing in industry could possibly come close to digging deeper into my research projects that I've started on.
When you go to the industry, how do you silence the voice that tells you you could be spending your time advancing the knowledge of humanity, rather than devising new ways to make people look at an internet ad, or helping big stock exchange companies aimlessly move money from account A to account B, without any net gain for the world?