Unlike QB and WR, RBs aren’t terribly correlated with QB success, at least fantasy-wise. In fact, in Barkley’s rookie season, where he finished as THE RB1, Eli Manning was dreadful (who remembers all those ridiculous dump-offs throughout the year?). Barkley, when healthy, is a top 3 RB in the league, talent-wise, so his RB3-RB5 ADP is surely warranted in my opinion.
Furthermore, fantasy QB success is heavily dependent on TDs and rush yards (generally speaking), and while Jones offers a bit of the latter, he only scored 12 total TDs last season. He just isn’t very good. However, he did show high upside in his rookie season, so maybe he can rebound from an awful sophomore campaign.