I spotted this project from Koichi Nakamura
A mother board approach to a Pi Zero cluster
Yes Andy stick 30++ PI Zeros which are either unobtainium or £30 ea from Cool components then stick them in an expensive carrier board then you too can have a cluster with the same compute power of an 5 year old Atom CPU 
Nice toy but Clusters of RPIs are a joke and merely noise to stop us looking at any number of much better boards out there!
Or have a 'Zero amnesty. Because maybe a whole load that were purchased are lying unused!
Mine is unused but (like many others perhaps) it is there for a "rainy day" - not really for any educational use.
(despite the amount of rainy days here.. wonder when I will finally use it.
Their generosity knows no bounds. :)
Don't think there's any money in it so really no great urge to chase after the remaining stocks!
I'm not sure that this still holds for "production of the pi zero". It could be that the foundation now has a separate deal with the Sony FAB to make the 'zeros, and that those being produced are being shared between pimoroni, farnell, pihut and a few others......
Other thing is that if you can only buy one at a time then a RPI Zero is actually £10 =£5+5postage and you need to repeat that for each of them