re: Chain deck ZTR for $5k?

I would say not at all, unless you are going to set the deck to free float. ...which they are not intended to do. The Scags I run have decks suspended by chains. They tend to become unlevel quicker than the Kubotas that rely on solid threaded bolts. The anti-scalp rollers are there to compensate as a last resort. You have to get into some big bucks to get actual free-floating turf decks, like Toro or Jacobsen mowers.