OL Coach Vs RB

Just an observation at this point of time, but I wonder why the value of a stud RB can be maintained whilst a team like the Broncos can turn an unknown RB into a household name on a continual basis. Its well known that the OL coach that was there has instituted a blocking scheme that breaks holes for the RB on a continuol basis.

The question Im asking is...... "Why not pay a large amount for an innovative coach that can get a late round pick 1200yds than pay for a 1st round pick that will get you 1400yds with the same coaching... those millions could come in handy (to build me a new house), or even build a better team.