Taking GP’s example of a $180k townhouse vs. a $1.8M McMansion, will these costs really be significantly more than an order of magnitude more expensive for the

Taking GP’s example of a $180k townhouse vs. a $1.8M McMansion, will these costs really be significantly more than an order of magnitude more expensive for the latter, and therefore significantly higher as a percentage of property value? My intuition is that the opposite would be true, i.e., that the difference would typically be less than a factor of 10.