Character issues aside, what makes you think this guy's going to be a bargain?
If he were willing to play for cheap, NE would keep him. As it is, they're likely to franchise tag him just to keep him around another year. Plus, why would Talib leave a successful team-- the hands-down favorite to win the division again next year-- where he's already learned the scheme and knows he fits in? Why would he play in Miami unless it's for the big bucks? Miami may be a team on the rise, but there's no guarantee of how it's going to turn out. Meanwhile, his current team still has at least 2 or 3 more playoff years to come. Plus, there are plenty of other teams would also be in the running to jack up his price, if he decides to walk away from the Pats.
It's not impossible that Talib would play in Miami, but the Dolphins would have to pay big money to get him. No way is he going to be a cheaper option than Smith.