Why is an artificial turf football field cheaper in other states?

“The Lewis Central school board is expected to sign off Monday on plans for artificial turf at the school’s football stadium.
The board agreed at its March 5 meeting to accept a low bid of $864,614 by M. E. Collins Contracting Co. Monday’s meeting will finalize the deal, since “only the school board can enter into a contract,” district Superintendent Mark Schweer said.” 

http://www.southwestiowanews.com/council_bluffs/news/article_1bacd472-708e-11e1-8689-0019bb2963f4.html