I cannot question the answer without more information, such as what is being replaced, what kind of quality and features will go into the replacement, and where is it. I strongly suggest you contact a couple of licensed contractors in your area for estimates. If you don't know any, ask your friends and neighbors for referrals.
Replacement costs vary enormously so get at least three estimates, in writing.
If you are attempting to price an unusual property using the cost method, your best bet is to seek out a qualified appraiser for your area, and work with a Realtor familiar with the type of property.
Best of luck,
Coldwell Banker Trails and Paths