Not to get involved in this little argument, but I agree that money is a factor a lot of the time.

"Money is the one thing that people say they argue about most in
marriage, followed by children (Stanley & Markman, 1997). But, there is
a lot of reason to believe that what couples argue about is not as
important as how they argue (Markman, Stanley, & Blumberg, 1994)."
-- From a September 25, 1998 posting on the Smart Marriages Archive, probably by Scott Stanley