it is hw selling business even though most expensive part is building and maintaining sw.
The software is not the most expensive part of a dive computer. For most manufacturers it is a "write once" process. With a few exceptions, most DCs have extremely primitive user interfaces and rely on code that is very basic. I suspect that the largest manufacturers have not modified their code in years.
Apple has taken 99% of the real costs out of DC production, perhaps excluding insurance costs. Legacy DC manufacturers do need to figure out how to create a mobile app -- which is generally more sophisticated than most current dedicated DC firmware -- but they will get there. Hopefully some independents will as well. I would love to see the team behind SubSurface come out with a Watch extension.