It really should not matter what size the pipelines are. You will not see them, they'll be under the surface. I think your concern should be: will all three lines be laid at one time? If they are laid at different times this will add to more use and disruption of your land.
A 50' ROW at $577.50 per rod for first offer is probably normal. It many times depends on the location and how bad they need your land.