It might be worth $4000 if it was an authentic piece of architectural salvage, but the straight edges suggest that it is composite or cast stone decorative piece.

You have a Greek or Roman Capitello and columns piece of art ,if the price would have been that much the person who sold you the house wouldn't have left it behind :) you could use it if you like to decorate an atrium or as a garden piece on your walls ,just think of Greece and old Rome architecture and make this piece part of your decor ,its rather interesting .
http://capharnaum.c.a.pic.centerblog.net/8tcvxi03.jpg
http://www.chocoladdict.fr/wp-content/uploads/2012/05/rome-antique-9-452x600.jpg

I actually found half of the wall decor at http://www.55downingstreet.com/wall-art/set-of-2-corinthian-column-fragment--wall-decor__m0145.htm for $800.00.

It's listed as a Corinthian Column Fragment Wall Decor.

I see it currently listed at $1,270.00 at: http://www.statue.com/Products/Architectural-Elements-and-Fragments/Corinthian-Portal-4-Pc-Wall-Frieze.html