In management accounting, everything has a cost that has to be quantified, regardless of whether it's a standalone product or part of a HW/SW bundle. At the most basic levels, you have revenue centers (iPhone unit, iCloud unit), and cost centers (Apple Maps unit, customer support unit). All of these have operating costs.

The only way Siri does not lose Apple money is if there would be materially fewer iPhones sold if Siri was eliminated. In other words, if Siri is not a product differentiator, it's likely losing money (in the management accounting sense).