First, the benign scenario relies on the transfer of productive resources across sectors - in particular, it involves primarily the inflow of resources into the residential construction sector. Presumably, the transfer of these resources entails some costs - retraining and perhaps relocation of workers, a different mix of capital, and so forth.
If residential construction were eventually to shrink as interest rates rose, further costs would be incurred as those resources shifted yet again to different uses. Another possibility is that the reality of the housing and consumer durables booms may not work out as neatly as the benign scenario would suggest.