First off, the 'fleecings' have been grossly overstated in this thread. We are talking about maybe 2-3 deals that could possibly be construed as such.
As for the offseason, why make trades when you have the cash to sign whoever you want? As JHB mentioned earlier, there isn't the dearth of talent in the offseason that there is at the trade deadline.
But for the sake of argument, let's take a look at a few offseason trades in the same time span:
Jaret Wright and cash to O's for Chris Britton: Getting anything for Jaret Wright is a win.
Randy Johnson and cash to Arizona for Luis Vizcaino, Ross Ohlendorf, Alberto Gonzalez and Steven Jackson: What Vizcaino did alone makes this a win for us. Ross contributed some and then helped us land Nady/Marte. Win.
Tyler Clippard to Nats for John Albaladejo: Wash. Maybe Clippard turns into something and this becomes a loss. Too early to tell.
Gary Sheffield to Tigers for Anthony Claggett, Humberto Sanchez and Kevin Whelan: Short term loss, although Sheffield is decomposing in front of our eyes. If Sanchez turns into the pitcher most project him to be, this is a win.
Ben Julianel to Marlins for Ron Villone: Ben who? Win.
Tony Womack and cash to Reds for Kevin Howard and Benjamin Himes: Neither Howard nor Himes ever made the majors. The Reds got 18 ABs out of Womack. Still, it's a slight win for the Reds.
Still looks like Cashman is maintaining a winning record, albeit not a perfect one. He trades aging players with value for prospects (long-term philosophy). He includes cash in deals to get better players in return (significant cash advantage). These aren't just cliches; they are exemplified by his transactions.
In the words of JHB, "There's no trade that, using hindsight, shouldn't have been done."