They are just changing the inserts though, how much can that cost?
Nope, they'll also need to completely redesign all the internal stamped metal parts for the electrical contacts, and also probably have slighly different moulds for the main housings to accommodate those and the necessary isolation barriers. Also, to me it doesn't look like there is enough depth for the European (Schuko?) pins in their render, so that is another variation.
Then they'll need to pay many times for the various country safety tests, which is significantly more than an unintentional radiator test. Plus product liability insurance in each country they intend to sell into (They may try to bypass this for KS.)
They appear to have the electronics and software prototypes, and 3D printed samples of the housing, and think that taking it into mass production is simple - e.g. see their reply in the comments re certification. Although they have electrical engineers on the team, it doesn't sound like they have actual experience with product manufacturing.
Why does it need BT, WiFi, Zigbee, Ethernet, and Powerline networking. Surely you're better off having them independant for "future proofing". Also, I'm not a fan of them using metal buttons on a mains powered device, even/especially if it is prototype.