Some of the costs probably will decline – some won’t. Developer profit margins will be the first to go, followed closely by contractor overhead margins, as the builders try to keep their machine intact. Land prices will hold on for a while because most of those sites already have an existing use to provide some cash flow in the interim. Hard costs will be the last to fall; and the fees, permits, financing costs, marketing costs, etc., will probably stay the same or possibly continue rising.
The high-$200s for those inferior units would still provide the developers with their original profit margins. Those prices could go to the mid-$200s before those developers started to actually suffer a loss. I think the high rises are actually at risk of suffering even greater losses (percentagewise) because in terms of utility they will still be competing with the lower priced units. Too many units and not enough buyers at these prices.