It seems off how RB's make so little compared to other WR's. But the simple truth is that position is over-saturated with talent with average-above average talent. On the flip side of that, your point still stands. Barkley is a RB talent unlike any other RB currently in the league (and may soon be joined by Jeanty). So it stands to reason he should probably make 20 or so million a year. But teams would rather spend more in other positions because they are not saturated in talent.
Its crazy. Yes. But coaches follow trends in the market. The market is wrong. That much is clear and we're seeing it first hand the difference a top talent at RB makes on a good offense that has passing and blocking talent vs an offense that doesn't have passing or blocking talent.
And right now, every coach and GM in the league is looking at Barkley, and what he's done for the Eagles offense and saying "Oh". Barkley may doing exactly what's needed to get the market to pivot a bit more towards a focus on top tier RB talent just like it has for QB, WR, EDGE and CB's.
You have to remember, it wasn't long ago that offenses thrived off of timing offenses with a plethora of what may just be considered the golden era for NFL QB's. During this time RB's weren't needed at a premium because it was so easy (or the QB talent was so commonly good) that offenses were moving the ball just fine passing. Now they're not and we're seeing offenses pivot back into running the ball more.
Its a game of rock, paper scissors that plays out very slowly. But its still rock, paper scissors none-the less. RB's are coming back into flavors of the year.