A new environmental impact statement shows the 21-mile stretch between Bloomington and Martinsville could cost between $500-546 million.
Last year, that cost was estimated to be between $405-440 million.
An INDOT spokesman says the previous figures were from a study done twelve years ago.
State officials still need to take or buy 346 acres to complete the section and it's unclear how the state will fund the work.
Most of the nearly $4 billion received from the toll road lease has been spent or allocated.