HS2, under construction in the UK, is 155 miles long, with a total budget of £55bn but currently expected to cost well over £80bn - some estimates have it as north of £100bn. $1bn per mile is in the same ballpark.
In the UK everything costs twice as much as originally estimated and takes twice as much time. I hope I will live to experience the 330km/h (operating speed of UK's HS2)