I think this is more the route they go. I think there's generally a nice sweet spot for RB value in Rounds 3, 4 and sometimes 5. You can get talented, productive impact players there, and there's not many positions that's true of, as far as the 4th and 5th go at least. Interior OL is probably the only other position I can think of where there's guys who can start by Year 2 consistently available after the 3rd. RB is also a position where you can platoon, and develop a complete skill set across 2 or 3 players at the position. Not the same as having one complete every down guy, but comes at a much lower price.