it may not help

It doesn't help the problem if they spend so much money on their lavish lifestyle.

It refers to "their money".

I read "It" as "their fears."

Indeed, for all their riches, some 40 percent of millionaires fear that their standard of living will decline in retirement and that their money will run out before they die, according to Fidelity. Of course, it may not help if their lifestyle is so lavish that they’re barely squeaking by on $400,000 a year.

The wording isn't the best, but try it this way:

Indeed, for all their riches, some 40 percent of millionaires fear that their standard of living will decline in retirement and that their money will run out before they die, according to Fidelity. Of course, their fears may not be helped if their lifestyle is so lavish that they’re barely squeaking by on $400,000 a year.

How would you replace "it" with their money, Roger?

Of course, their money may not help if their lifestyle is so lavish that they’re barely squeaking by on $400,000 a year.

I don't know. You could be right.