I sold my medium for £250, but that was before the pandemic when they were still available new.
Prices seem variable, I saw a complete bike on the ebay completed listings sell for something utterly ridiculous like £280. At the same time I wouldn’t have said £300 was a bad price for the frame/fork/headset (say in good condition with a Chris King headset), maybe £200 if it needs a respray and no/a generic headset.
It’s a tiny market, so either you find a buyer who’ll pay over the odds because they really want one and one only comes up every few months. Or you put it on ebay and no one bids because there isn’t that 1 buyer.
Full bikes, hard to say, even if it was a bling build, it’s still going to mean QR hubs, not boost, not tapered, older groupset. So there’s a limited market for splitting those bits and/or a buyer could buy them as bargains themselves.