original_query: What was the value of the board mentioned in the text?
query: What was the estimated cost of the Doncaster rail line at different times?
answer: Cost estimates for the Doncaster rail line varied significantly over time.  Estimates ranged from $41 million in 1972,  $73 million in 1974,  $120 million in 1975,  $336 million to $471 million in 1991, $1 billion in 2006, and $3 billion to $5 billion (plus additional costs for extensions) in 2014.