This NY Jets-focused site compared the salaries of running backs to their production.
It combined 'points' assigned by FootballOutsiders and Pro Football Focus, and divides a player's annual salary by that number. This gives you a bang-for-your-buck metric on a per point basis and as a total for the season ($/pt x total points).
Frank Gore Costs $97k per point of output, 52nd in the NFL out of 63 eligible backs. Brandon Jacobs cost $93,500 per point of output, 48th in the NFL.
Keep in mind that there is no relationship between $/pt and total points, i.e. backs who produce more points do not necessarily get paid more.
Compared to backs who produce similar numbers, Gore appears to have an average cost. Jacobs, on the other hand, was 'overpaid' for his production. We hired him for half the cost (or less), so we should be getting *really* good value our of him.