What things are worth is whatever people will pay for them. It doesn't matter what others think they are worth, it's their worth to the buyer. It doesn't matter how long they are in the tooth if that's what the buyer wants. I prefer the B+ for what I do.
It seems ridiculous to me to say a B+ with what it offers is worth virtually nothing because a Zero without most of what the B+ has to offer costs a fiver.
The price seems in line with what I've paid for various Pi not too long ago.
I would bid at £20, would likely buy it now for £30, if it were not for the fact I don't do ebay.
I was trying to calculate the value of a B+. The way I use them requires monitor, keyboard, mouse, wired LAN. A Zero is £5 but needs adapters, plus a USB hub, plus a LAN dongle. That's going to add up to another £5 at least. That all comes with a B+ and better packaged so £10 is reasonable to me.
A 2B is about the same, and there's a free B as well. I don't see it's an unreasonable price to ask though others are free to disagree.