"Software is much easier than hardware. If you are to start a project today in this kind of hardware, you will be operating it in 2029, without changes."

I don't think this makes sense, you are using the three statements "Software is cheaper", "Software takes less time" and "software is easier" as if they all mean the same thing, and proving one means proving all of them.

Hardware takes a long time, okay, that does not mean it's expensive. Building a hydroelectric dam takes 20 years, but it provides the cheapest source of electricity that ever existed. Ships can take a decade from order to delivery, they are the cheapest mode of transport.