A real conversation I was involved in:
Product Manager: the system must have feature XTZ
Developer: this will push the release date by at least two weeks
Product Manager: I'm not discussing the schedule, the schedule is (developer manager) responsibility, the system must have feature XYZ
In this particular company the "product team" is responsible for designing the product but the schedule (and cost) is the responsibility of the development division.
This causes the product team to dream up a very complicated and detailed product, this also causes them to be unwilling to compromise on anything - because they are completely insolated from the cost of building their design.
Can you imagine the same dynamics in a car manufacturer?
Car designer: The car should have A, B, C and D
Factory manager: It will cost more to build this car then what we can sell it for
Car designer: I'm not discussing costs, the costs are not my responsibility, the car should have....
Product design isn’t coming up with ideas, product design isn’t building plans to make those ideas come true and product design isn’t making pretty graphics.
Product design is taking all the constraints (and if you ever want to be profitable your budget and time-to-market are probably your two biggest constraints), thinking very hard about the tradeoffs and making painful compromises in order to create the most successful product possible under the circumstances.