There is a small savings in cost, but IMO the C1 isnt revolutionary by any means, and will ship almost a week later than S3+ units will (which is a ~$20/0.05BTC difference)
Theres a higher risk of leaks and failure with this design i think, and for most people taking up slightly less space, with a large rad dangling someplace, wont offer much benefit as the S3+ is fairly easy to stack on its side anyways.
If someone can point to a 5kW-sized radiator/pump that could run multiple C1 units in parallel for under $150 though, thats a different story
There will be some kits soonish for multiple units, but generally you can't put 5kW of heat in an arrangement like this [easily]. Coolant temps would be too high by the 5th unit, and the head pressure required to go through 5 sets of waterblocks would require pumps in series which is never a great idea. Remember the tube cross section is pretty low, so the minor losses become significant if you try and increase flow rate significantly - which is what you need to cool 5 units on one loop.
For now, the shipping on the second individual kit for now is only about $15, so you get the entire kit delivered for about $65.
hence why i think parallel tubing with distinct pumps but a common radiator (using a large 480mm, 1000cfm fan or similar) would be slightly more viable to transferring heat.
either way, for most users this seems pointless unless you either circulate the hot water into something useful (like heating a pool) or can easily hook 20+ of these units up and be able to transfer the heat 20 feet or so to a convenient opening.