You have to factor Sturm into the equation. He makes a good living now. Why would he take the fight for small money?
That is a woeful offer; bear in mind that Pavlik only made $1m out of the $2.5m purse for the Lockett fight after expenses, so he'd make only $400,000 from this fight. Of course, it would be nice if he swallowed his financial pride and took the fight anyway; most people wouldn't see that kind of money in their lifetime. So yeah, he "should"; but it's unreasonable to expect him to.