So Blue Jays general manager J.P. Ricciardi said last week he’s open to trading Roy Halladay. And Halladay said Monday in St. Louis, where he’s preparing for tonight’s All-Star Game, that he’s open to getting traded to the Yankees.

It’s nice to see so many open minds out there.

One mind that is probably not open to trading for Halladay is Yankees general manager Brian Cashman. Even since passing on Johan Santana — a mistake he won’t admit to — Cashman has held fast to this principle: He won’t trade his best prospects for a player and then give that player a rich contract extension.

It’s a perfectly logical stance. If you’re the Kansas City Royals. Or Pittsburgh Pirates. Or maybe even the Mets after Bernie Madoff got done “investing” the Wilpons’ extra cash.

But not if you are the New York Yankees.

Cashman didn’t have any problem throwing cash at CC Sabathia and A.J. Burnett this offseason, then didn’t flinch when given the opportunity to swoop in and steal Mark Teixeira away from the Red Sox.

But don’t kid yourself: It wasn’t Cashman’s deft negotiating style or Teixeira’s boyhood love of Don Mattingly that got the deal done. The Yankees offered the most money.

How does that apply here? Well, the Yankees can’t flat-out offer the Blue Jays money; baseball isn’t soccer. And Toronto would probably insist on a higher haul of prospects from a division rival, making it more likely they could complete a traditional players-for-players deal with the Phillies or Angels or Dodgers.

What the Yankees can do is what they should always be willing to do, what they are always able to do, and what they should be ashamed not to do considering the prices they charge:

Flex their financial muscle.

Make the Blue Jays an offer only they can make, not by offering money but by taking money — a lot of it — off Toronto’s hands. See whether the Jays’ desire to save cash is more powerful than their desire to save face with their hockey-loving, LaBatt-swilling, bacon-eating fan base.

Tell the Blue Jays they’ll take Vernon Wells and his mega contract in addition to Halladay. Wells, 30, is due nearly $110 million through 2014 and is not worth it, not that anyone is.

Still, he’s one of the top five centerfielders in baseball and way better than either Brett Gardner or Melky Cabrera. He has a no-trade clause and can opt out of the deal after 2011. He would be crazy to since he’s guaranteed $21 million a season after that.

What do the Yankees offer Toronto in terms of players? Gardner or Cabrera, Ramiro Pena, a couple of lower-level pitching prospects, nothing more. Remember what the Mets got Santana for? And they didn’t take back a second big contract.

Now for the biggest question: Should the Yankees do this?

Yes, if their goal is to win the World Series. Because as they are constituted now, the Yankees are the third-best team in the AL after the Red Sox and Angels, neither of whom they can beat on the field.

But when it comes to the checkbook? There, the Yankees can’t be beat. It’s an advantage they have to be open to using once again.