Earlier this afternoon, Dave Glenn spoke to Baseball America's John Manuel about Russell Wilson. Manuel said that the Rockies "do signability very, very well" and that they are "not going to approve that pick if they aren't going to sign the guy." Not surprising. The Rockies aren't going to reach for a guy with signability issues if they aren't willing to shell out.
The first step in attempting to ballpark Colorado's offer is to note that "Major League Baseball recommends bonuses for each pick in the first five rounds." When you hear the phrase "slot money," that's what people are talking about. Since they're just (strong) recommendations, teams are free to exceed those amounts at their own discretion. The Rockies may very well do that with Russell Wilson--fvpackman thinks Wilson's deal will exceed $500k, which would be above slot, and his guess is as good as anyone's.
Based on the sparse figures I've been able to round up, my guess is that the recommended slot money for the 140th pick is in the neighborhood of $300,000. So Wilson's negotiations probably start thereabouts.