Hi BrainStorm
The method of estimation of The Chemical Eng. Plant Cost Index,and others, can not predict the cost in the future, but it can do it for the last year.
After you apply it ,you will have an idea of how the prices could be at the present time.
Economical engineering and Che.Eng. Plant design, were the name of one of the courses, related to this matter that I had studied at the University.
The best book: Peters and Timmerhaus, "Plant Design and Economics for Chemical Engineers", 4th ed., McGraw-Hill, 1991.
I think you should review your old notebooks and remind.
Good luck