Gartner Research: "A locked and well-managed desktop PC can cost 43% less to keep than an unmanaged one." ~Desktop Total Cost of Ownership: 2011 Update, Gartner RAS Cor Research Note G00208726, Federica Troni, Mark A. Margevicius, Michael A. Silver, 16 November 2010, RV2A612011
(My experience has been consistent with this.)
More:
https://www.google.com/webhp?q=laptop%20vs%20desktop%20cost%20of%20ownership#q=laptop+vs+desktop+cost+of+ownership