This is a cool idea, and I was really interested to see it be done, but I wouldn’t actually do this. There are a lot of parts to this just to have cheap colo, and I would be worried about failure of the components like the usb hubs taking down the cluster. you can get a Mac Mini colocated for $54/mo with 24/7 remote hands, a dedicated ip, remote power management, and gigabit uncapped bandwidth, which is much better hosting than that $30/mo offering, so you’re not paying more for nothing. An M1 Mac mini with 16 gb of ram and a 1 tb SSD is $1300 not on sale. From a cursory google of benchmarks, an M1 on geek bench is about 11x more powerful than a raspberry pi 4b, so you are getting much more compute. Also, the 16 gb of ram is directly integrated with the processor, there is no need to manage multiple nodes, the hardware is battle-tested, it has true gigabit Ethernet, and the people at the data center also understand the setup and can repair it for you easily.

I guess what I’m saying is - super cool that you did this (and I have a cluster of pis at home as well to play with, I love them) but if I was going to pay for colo, I would just colo a Mac mini.