Directly powering all components would require to plug 6 (cluster nodes) + 1 (cluster server) + 1 (switch) = 8 wires! Added to the cable mess it would imply inefficient powering with at least 6 low-cost power adapters.

Luckily, one can find on E-Bay used power units from decommissioned servers. Not only it is an affordable way to use professional-grade devices but also it is good for the environment since reusing old parts is better than producing new ones. In addition, efficiency of such power units is far better than the low cost ones usually found for domestic use.

I found a tested 12V/1200W(!) server power unit for 25€ (shipping included). It will power at least cluster nodes and, if possible, the whole cluster.

A USB Power adapter is soldered to the power output because, whatever the chosen architecture (ARM/X86_64), cluster nodes are Small Board Computers fed with USB power.