Why ResMed has so many models?

[MyronH]

I'm wondering why ResMed don't incorporate some features, that are obviously just software based, to other models?
For instance, the vAuto vs the ST that has the backup rate. Surely that feature is just software alogorithms they add to the machine. I would think the vAuto would be capable of having the backup rate as well.

[Walla Walla]

Because they want to be able to charge extra for the backup rate. They know the government wouldn't pay for a machine with backup if it wasn't needed.

[JesseLee]

Money.

[tedvpap]

All machines are mechanically very similar - they have a blower and two sensors (flow rate sensor and pressure sensor). The differences are due to the programming.