Saw lower rates when considering my trip to Prague but rates jumped when I looked after booking airfare, so hoping some site might still have old rates. Only thing I've found in looking for a LNF so far is a non-refundable on a Deluxe room, but that's not even offered on Marriott.com.

Prague Marriott Hotel, November 20-24, 2015

Deluxe Room
Fri, Nov 20 - 3900 CZK
Sat, Nov 21 - 3900 CZK
Sun, Nov 22 - 3500 CZK
Mon, Nov 23 - 4100 CZK

Total Room: 15400
Room+Tax: 17710