Once software is "done" (we all know software is never done) you can just copy it and distribute it. It is negligiblehow much it costs to do so.
Once hardware is done you have to manufacture each and every piece of hardware with the same care, detail and reliability as the first one. You can't just click copy.
Often times you have to completely redesign the product to go from low volume high cost manufacturing to high volume low cost. A hand made McLaren is very different than an F-150.
The two simply scale differently, by nature of their beasts.