Surprisingly, BP was actually thought it was a good move. I was prepared to get skewered again like after the Ceda deal.
Cost: Technically, it isn't a straight $52 million over four years, it's three years for $34 million and a 2012 player option for $14 million. To pick a few unfair comparisons, that's not Zito money ($18.5 million in each of the next three years, plus another $19 million for 2012, and then those other two years), nor is it even Suppan money ($25 million for the next two years, plus either another $12.75 million for 2011 or a $2 million buyout). It's a lot more than Lohse money ($41 million over the next four years), but that's Kyle Lohse after the best year of his career (5.4 SNLVAR, a 44th-best SNLVA Rate of .566) as opposed to Dempster after the best year of his (6.8 SNLVAR, and MLB's 11th-best SNLVA Rate of .611). More precisely, it's Meche money ($35 million over the next three years), and Meche seemed to have a whole lot less going for him after the 2006 season than Dempster has going for him now.
So in terms of the expense, it's reasonable in light of the market, and it's a whole lot less than what Derek Lowe's going to command starting next year in his age-36 season, let alone what CC Sabathia's going to run you. If there's a relative financial risk that might have been worth running instead, it would have been trading for Jake Peavy, because Peavy's going to run his employers $60 million over the next four seasons if his 2013 option isn't picked up, and $78 million over five if it is. That's close enough to make you say hmmm, but where Dempster only cost you money, Peavy would cost you money and the talent to acquire him from his employers. Felix Pie, for starters, and who knows what else, and while you've got ready-now fourth starter types to spare, the Padres need prospects, not Chad Gaudin, and the Cubs don't have many prospects. So even there, the math's understandable, especially once you move on to...
Risk: Let's give the man his due, he's now several years removed from a surgery-affected season, and the damage that Jim Leyland visited upon him almost a decade ago. This year's funky new glove wiggle aside, Dempster's motion doesn't seem unusually risky, and if anything, it appears he was throwing more fastballs working in the rotation than he had been as a reliever. As opposed to betting on an especially unusual body type (Sabathia) or value from a guy up to and perhaps beyond his 40th birthday (Lowe), you're banking on a player who's been relatively healthy the last several years staying so in his early to mid-30s. That doesn't seem all that unreasonable.