The $500,000 ransom in 1956 would equal over $4,800,000 in 2021.
This film was based on Fearful Decision (1954) (of The United States Steel Hour (1953)) that first aired live on June 22, 1954. It was so well received it was re-staged on the show again (Fearful Decision (1955)) on May 10, 1955. This film was remade by Ron Howard as Rescate (Ransom) (1996) starring Mel Gibson.
The $25 bonus paid to the bank workers would be about $240 in 2021.
This film was a success at the box office, earning MGM a profit of $336,000 (about $3.25M in 2021) according to studio records.