This is the example he gives for a Bitcoin node:
Target hardware resource cost: $200
Target worst case time to validate a block: 10 seconds
Minimum network I/O: 2 Mb/s
Minimum disk I/O: 2 Mb/s
Minimum CPU: 5,000 MIPS
Minimum RAM: 1 GB
The definition of a "node" is different though. You can indeed run a non-mining Monero node on a Raspberry Pi 1B if you really want to. Total hardware cost: ~$30.00. There are even cheaper options available that are faster too, like the PINE A64 for $15.00. What exactly are you trying to specify?
It is meant to spec a non-mining full validating node on the Monero network.
The idea is to establish a goal that a monero node should be able to validate a minimum of N TPS, and the hardware needed to do that should cost no more than, say $50. This value would represent the minimum hardware needed to process the stated number of transactions.
And then, when evaluating changes to the protocol we could have an idea of how those changes would influence the number of nodes on the network based on the impact it would have on $$$ needed to setup a node.
The value of the hardware is not the only thing that matters, of course, but it is an important one.