High-income people live farther from worksites because the neighborhoods are nicer there. This argument has an element of truth to it, but it is putting the cart before the horse. In the most basic sorting models, including Gridcity, neighborhood amenities do not matter. High-income people live farther from worksites because they have a higher utility level. This argument is simply wrong.
Utility has nothing to do with it.
The utility level simply indicates the quality of a group's opportunities in other areas and says nothing about their relative bidding power within the urban area mapped by Gridcity. The utility level has no impact on the slope of a bid function and therefore cannot affect sorting. This version is technically correct, although a bit cryptic. A group that does not require a large drop in housing prices to be willing to live far from a worksite, as indicated by a relatively low ratio of t to H, has an advantage in bidding for housing at more distant locations. Because housing demand, H, tends to increase much faster as income increases than do commuting costs, t, high-income people tend to have a relatively low ratio of t to H and hence tend to win the competition for housing far from worksites.