The price includes the necessary PCB parts, connectors, wiring and software settings.
If the power supply fails, all dump loads go off, and the generator will speed up. This can be potentially dangerous, depending on how overspeed-tolerant your generator is.
With a second power supply, the dump loads will stay on, even if the first power supply fails.
The hydrocontrol will display a warning that the first power supply failed.
If you have a12/24V DC battery power supply on site, this second power supply can also be powered by 12/24V.