Comparing the 1925 silent version of Ben-Hur with the 1959 remake

At the time of their release, both the 1925 and 1959 versions of Ben-Hur claimed the title of most expensive movie ever made, costing $4 million and $15 million, respectively
https://en.wikipedia.org/wiki/List_of_most_expensive_films#Record-holders

The budgets for the various film versions of Ben-Hur, adjusted for inflation to 2020 dollars:
1925 Ben-Hur: $59.65 million
1959 Ben-Hur: $133.43 million
2016 Ben-Hur: $109 million

I think it would be really interesting to see a detailed budget breakdown of why the 1959 version of Ben-Hur cost so much more than the silent version. Obviously having to record sound was an added expense, but the 1925 film was famous in its own right for cost overruns

You might think increased salaries for actors would be a big factor, but Charlton Heston was paid $250,000 over 30 weeks for his starring role in Ben-Hur, while in the 1920s silent Ben-Hur star Ramon Novarro was making $10,000 a week

Filming the chariot race: 1925 Ben-Hur and 1959 Ben-Hur