Agreed, Paulinho is typical domestique, who has no chance of podium ever, so it's more important for him to get a decent contract and get in a team that will do well. However for riders like Tony Martin, Wiggins, they also weigh the factor of whether they will get team built around them to win the Tour (and that's why Martin turned down possible deal with the Shack, because he knew he wouldn't be the leader, at least not in 2010).
for a second just think if contador is not 1st, then astana only has 3rd place and 6th, which is no batter than saxo 2nd and 5th. so having contador this year makes a huge difference in pay (at least in the Tour), though they could probably still manage a team win, but the payoff is different (i believe you only get 20k for team win vs. 400k plus for overall yellow jersey)...