Looking for good used parts can save you plenty of money for other things.
Amen!
I have a tendency to buy refurb PC hardware (except for PSUs and HDDs!) for just that reason. Though, I really try to do "factory refurb". (I've bought factory refurb SSDs and WD HDDs, that showed zero POH, so I think that they were new-old-stock, being sold as refurb, which happens sometimes. They do that so that they can sell old or "RMA reserve" stock, without having to offer a "new product" warranty on them.)
I had a recent semi-bad experience with an Acer 1440P IPS 25" or 27" monitor that I picked up off of ebay, it was NOT "factory" refurbed, but "our 3rd-party techs tested these to be good". Well, when I got it, it had lines running down the screen. I was going to return/exchange it (they offered 30-day returns, to their credit), but then, mysteriously, the lines went away, after the monitor was leaning on another monitor at an angle for a period of maybe a week. Then I knock the monitor off onto the floor off of the top of the PC it was on with my chair, and the lines returned. Then I ended up knocking it off again, and the lines went away!
So, obviously, there are some issues with the screen. Maybe a cold solder joint, maybe a bad cap, loose cable, whatever. I can't seem to figure out how to get into the monitor, otherwise I'd attempt to fix it myself.
But it was only $100, compared to like $250 new.
OTOH, buying "new" is no guarantee of proper functionality.
I recently bought some "CableMatters" RealTek-chipset USB3.0 Type-A 2.5GbE-T dongles, for a decent price, brand-new off of Amazon. (See my thread in Hot Deals for link).
Been having issues with it disconnecting, as I have with some other ones too. It might be my system, my PSU is slightly suspect, so is my Ryzen SoC USB 3.x support, because I let my CPU "cook" at 117C (according to Ryzen Master) for a few hours. (Might have damaged my SoC/CPU.)
Or maybe, it's just the length of the USB3.0 shielded extension cables that I'm using?
Could be a multitude of things, and unrelated to the actual 2.5GbE dongle, maybe.
Conversely, pretty-much all of my routers are refurb (mostly factory refurb), and they work well. They tend to work for years, in my experience buying refurb routers for nearly 20+ years. (Once, I had a bad power adapter for an AC68U/R/1900 purchased from Newegg as a refurb. $20 and a trip to ebay fixed that.)