Mattress Mack is hoping his family's generous contribution toward Mary Lou Retton's medical expenses leads to more donations for the Olympics legend ... telling TMZ Sports it's the least they could do.
Mack -- real name Jim McIngvale -- and his wife, Linda, wrote a check for $50,000 to assist with the gold medalist's hospital bills as she remains in the ICU with a rare form of pneumonia.
We spoke with Mack -- who owns Gallery Furniture in Texas -- about his family's decision to step up in such a big way .