Non believers . We don't waste money on churches.

Let's look at the richest guys in the North America:

Bill Gates and his family attend a Roman Catholic Church. Warren Buffett, raised Presbyterian, identifies as agnostic. Bernard Arnault is Catholic but doesn't attend mass. Carlos Slim Helú is a Maronite Christian. Mark Zuckerberg embraces his Jewish upbringing, while Larry Ellison, who was raised under Reform Judaism, no longer follows a particular belief system. Charles Koch is nonreligious, too.

Gates - Believer
Buffet - Non Believer
Arnault - Likely Non Believer
Slim - Believer
Zuckerberg - ??
Ellison - Non Believer
Koch - Non Believer

so it's about 50/50

That's much higher than the proportion of non believers in the USA which estimates range from 20% to 30%.

It's not surprising. Wasting every Sunday morning and 10% of your income every year would seriously cut into your chances to accumulate wealth.

Too many qualifications... many parts of the world, e.g. Asia, have different religious and theistic "rules" than we do, it wouuldnt be an apples to apples comparison. Plus, some people are "spiritual but not religious" and some are inarguably religious but don't have a spiritual bent at all. And lots of people who claim to be "believers" spend a huge amount of time deciding who is a "true" believer, and who isn't.

Anyhow, I don't think it's possible to answer that question, because between avowed atheists and avowed theists, is.... a whole bunch of other people.