Exactly. I did a lot of work for IDOT land acquisition in the past. What you say is true. ROW costs are often the top line in any construction activity - especially in an urban setting.
As my screenname suggests, I live in Medina. Medina today is a Cleveland/Akron suburb with a substantial portion of our residents commuting to work in either Cleveland or Akron. It wasn't always that way, the interstate system made it possible.
Medina is ~30 miles SSE of Downtown Cleveland as the crow flies. By car on I71 it is 32mi per Google Maps and Google says it takes 38 minutes. Off-peak you can do it in half an hour and at rush hour when I was working downtown I figured on an hour.
Medina is closer to Akron, about 25 miles and, pre-interstate Medina had more commuters to Akron than Cleveland. Today it is the other way around because there isn't a direct interstate to Akron so that ends up taking about as long as getting to Cleveland.
Anyway, to your point about ROW:
I know that I71 was completed from the Columbus area to Medina (SR18 specifically) sometime between 1958 and 1961. I only know this because my dad graduated from HS in 1958, spent three years in the USMC, and came home in 1961. He said that there was no I71 when he was in HS and when he got out of the Marines he drove home from LA (Twentynine Palms specifically) and the last leg of the trip was I71 from Columbus to Medina.
Then I71 stopped at SR18 for about a decade. Construction slowed because of the issue you raised, ROW in an urban setting. From Columbus up to Medina they were mostly building the highway through farmland so ROW acquisition was a fairly simple matter. Farmland has a more-or-less agreed upon per-acre price so ODOT simply drew up maps and went to the farmers with a per-acre offer. If they refused the matter went to Court (eminent domain) and the farmers were paid the appropriate price per acre.
Once they got North of Medina the process was MUCH more difficult. When they built I71 from Medina to the lake they took out literally thousands of houses and had to deal with a lot of ROW acquisition headaches. I71 stopped at SR18 in Medina for roughly a decade while ODOT worked all of that out.
