A slightly cheaper option would be to get a bunch of Pi Zero W devices. They're $10 + SDcards. They would rely on WiFi which might be acceptable if the use case allows having a few dozen radios chattering next to each other. If not, then a $5 Pi Zero + $5-10 ethernet adapter might work.

Since the goal isn't to achieve maximum performance, the slow CPU & RAM (comparable to a 20th century desktop) might not be an issue. And the lower price would allow more devices so you could test more complex configurations and server management options.