Well, at its face, a successful hit in combat is about 700KCr in repairs (this number swings wildly, they can go as high as 10MCr). A random free trader with 82 tons of cargo is, ostensibly, worth 82,000Cr, but since it's black market and fenced, it's worth, maybe, 40% of that. Perhaps there's some speculative cargo. That also assume they can take all of the cargo.
In '77 Book 2, a pirate was either a Scout ship or a Merc Cruiser. A Scout ship has to be maintained just like anything else, and we'll crassly assume that the ship is not being maintained by the Scout service. So, that's 11,300Cr every two weeks stashed in the bank for maintenance. But a Scout ship only has 3 tons of space, so 3,000Cr of cargo. Not looking good right out of the gate, and we're not including to crew (which we assume are working for shares, not salary). But there's also the life support costs. 3,000Cr of cargo aren't going to put a dent in those.
The Merc Cruiser is worse. 172KCr in Maintenance every 2 weeks. At least the hold can hold 80 tons of the cargo.
Still a losing proposition.
Obviously they cherry pick the finest goods, but even then they don't get full rate for them. It costs time and money to funnel goods to the shadier trade bazaars of the Imperium.
Of course if they're ripping ship parts out of their victims (power plants, computers), those should be valuable and fungible. But certainly take more time to remove than handy, prepackaged cargo pallets an containers. Plus whatever petty cash, jewelry, and watches they may get from the passengers and crew.
But ships are expensive to run, fuel, maintain, and crew.
