I don't think that consultants are the only reason why transit is so expensive. The United States tends to have a lot more regulations and community feedback to contend with.

The California high speed rail project is a good case study for this. They had to deal with a tremendous amount of lawsuits from people who didn't want rail in their backyard, and would often use any kind of legal mechanism to stop rail from being built in their community.

I mean, think about how the Red Line in the 80's already had budget allocated to extend to Arlington. If I recall, a significant portion of that tunnel was actually built (and still exists) before the good citizens of Arlington put the kibosh on a station in Arlington.