The first time a developer returns a negative ROI on capital, and fails to repay their loans, they cease being a developer. Developers don't have any money of their own. They borrow it from banks or equity partners. And if those partners don't like the ROI, they don't lend the money. Developers watch interest rates (and hence their cost of capital) like it's the world cup, because it's key to their business model - it determines what 'pencils', what can feasible be built with and ROI that covers their cost of capital, their costs, and the risk they undertake borrowing money in the face of appreciating construction cost and uncertain regulatory delay.