The idea that the Bonilla thing was a "Blunder" is categorically false.
The Mets basically put $1 million into a bank account* at the end of 1999, and added half a million to it every year for the next nine years. At year 10, the account had 16 million in it. Every year, the interest accrues and they pay it out to Bonilla each. So the Mets paid $5.5 million over nine years, instead of $5.9 million in 1999, and everyone wins.
Of course, the big problem isn't this maneuver, it's that the "bank account" the Mets put the money in was "Bernie Madoff's pocket."
Why did the Mets do the deferrment? The Mets wanted to add Mike Hampton ($5 million), but Houston wouldn't trade him unless the Mets also took Derek Bell's contract ($5.75 million). The Mets only had $6 million to spend and needed to free up $4.75 million. D eferring Bonilla enabled them to make the trade.
Mike Hampton had the 5th best ERA in the NL in 2000; threw 16 shutout innings in the NLCS to win series MVP, and led the Mets to the NL Pennant and a 2000 World Series appearance.
THEN when he didn't resign, the Mets got a compensation draft pick and took David Wright. The Mets won the trade by about 60 to 12 in controllable WAR.
And, by the way, the World Series loser's ownership share of playoff revenue is probably way higher than what they'll pay to Bonilla. The 2017 players cut was $30.4 million for the World Series losers, and that number includes less than half of playoff ticket sales (the owner's cut has the majority of it, plus all the in-stadium revenues).
Every team has deferred payments to dozens of players. The Mets are mocked with the Bonilla contract simply because the sports media just loves to rip apart the Mets. There's really nothing "special" about the Bonilla deferment at all.
It isn't the MLB record for most money deferred. Not by a long shot. (hell, the Nationals offered $100 million in deferments to Bryce Harper this offseason!)
It isn't the LONGEST deferment (The Yankees traded for a pitcher from the Cubs, the Yankees ended up spending $5 million court fees because the contract deferments legally required the Yankees to pay the pitcher for a longer term than the Yankees Owner Partnership legal entity was scheduled to exist. The Yankees had to extend their partnership (no big deal), but the Yankees had to pay a legal team to fast track the process and cover their behinds from the contract and trade being voided.
It isn't the most disastrous deferment. The Atlanta Braves' Bruce Sutter gets $1.3 million every year in deferments on a contract he signed in 1985. A total of THIRTY YEARS of deferments (for a guy who retired after 1989) and he also gets $9.1 million lump sum at the end.
The list of contract deferments in MLB is insanely long. The 2001 Diamondbacks had a payroll of $85 million.... with $250 million in deferred salaries!