The key argument against this is that many of the planned highways were also supposed to go through richer neighborhoods, but never got constructed because the

The key argument against this is that many of the planned highways were also supposed to go through richer neighborhoods, but never got constructed because the residents of those neighborhoods were able to successfully fight against them. (For one example, check out the incomplete stub at the eastern terminus of I-70 -- I don't believe the cost of the land was a major factor in that case)