After some messages between Me <--> Service Rep <--> Engineer, the quoted prices were $38.32 for 1pcs and $73.43 for 2pcs of the aluminium 3D print from PCBWay. The shipping cost hasn't changed at all, suggesting that the c8or r0 must have been just a bit too large and the system bumped it up to a bigger-package charge. 

Now it seems that all my "sweat equity" into shavings has synthesised into savings, as I can now buy 2 c8or r1's for about $2 more than a single c8or r0. 

In British Pounds, my cost for this specific order is approximately £64. 2^1 pcs of 2^3-channel heatblocks costing £2^6... what's the 2^10 going to be?