NC1200's crush this, so why bother? Willing to bet they choose ICEpower due to margins.
IcePower has been in the game longer and if, as a manufacturer, you're concerned with long service life it's a safe bet to go with the OEM with the longest proven track record. It's come up more than a few times that Hypex uses less expensive capacitors on their modules which could lead to a shorter service life. I believe ICEPower modules typically use Panasonic capacitors, which are generally well regarded.
It's certainly also possible that ICEPower is the lower cost option as you say, but I don't have the cost of OEM parts from Hypex or ICEPower handy, so I cannot confirm that.