The reason I put in $16K is that is what the Ferris website I found was selling them for with a 72" deck IIRC. $11K is better but I would think that anyone buying a huge industrial mower would want a diesel engine. Several makes of those front deck mowers, like Kubota and Toro in 4 wheel drive models.
Personally on my hills, 52" is a bit wide to prevent scalping.
EDIT: I went back and looked at that site on ebay and it was a 72" deck with a 30 HP Yanmar Diesel engine, so not so bad of a price after all with the diesel engine and 72" deck.