(this is also what the court found)
Also keep in mind that various kinds of price fixing by manufacturers (IE forcing retailers to sell at a certain price) are also subject to antitrust arguments. It's simply no longer "per-se" illegal. For a long time, the precedent was that various forms of price fixing and price maintenance were illegal on their face. YOu didn't have to prove it hurt anyone, only that it existed.
They are now subject to rule of reason analysis (basically, balancing of harms).
The reason such lawsuits are uncommon is not because the price fixing is okay, but because it is incredibly expensive and time consuming to litigate for a very uncertain outcome :)