Normally yes, but for example, I have an old laptop that the SSD finally hit its limit and died. The laptop was not worth putting more than $10 to $20 in, and I got an 850 EVO 250G off ebay for like $9 shipped. It had 7 or 8 TBW out of like 150 it is rated for. For something like this, that's a perfect use case for a used but not abused SSD. The laptop is still useful to me as it has a serial port and I use it for hooking up to cars and also in my lab for router console connections, so didn't want to trash it, but also didn't want to spend $50 on a new huge drive that would be of no benefit over an older one. I think the OP's use case fits that too, why get a brand new super fast and big SSD when you need a tiny, slow, older one (since the router can't keep up with even several year old SSDs anyway).
Or to put it another way, if cost is a factor and it comes down to spending $20 on a new USB drive or $20 on a used SSD and enclosure, I'd go for option B.