Firstly, when I have compared rates on FK vs Amazon, I have found FK to be overpriced (or maybe Amazon employs predatory pricing, whichever floats your boat!) in excess of 5k.
Its 38.2K on Amazon, not 36K.
Secondly, as mentioned, the extra 4GB and Windows 8.1 OEM copies are responsible for the increase in price.
They now a days use the same base for same series same dimensions - Dell guy.