Bowman is good. Timmons is better.
Comparing deals... maybe he likes being a 49er? Maybe they said 'this is what we can offer or look elsewhere'? Maybe Timmons has a better manager?
Maybe the Steelers value Timmons higher than the 49ers value Bowman?
Too many variables. What's the value of a player? Whatever the team he gets paid by is willing to spend on him.