Hi CF, welcome to the forum
The Dead Ringer single pic disc is not what you could call rare.
I've just searched on ebay and found 19 for sale
As Monstro said, I would expect a DR pic single to sell at auction on ebay for no more than a fiver (and even less than that).
You see some with buy it now prices much higher than that, and as my friends in the antique trade would say, "you'll die with that" (because no way in hell are you ever going to sell it).
Most of the time there will only be one bidder on the single or it will go unsold.
On the other hand, I would say it may worth looking at the Dead Ringer album pic disc.
A little rarer than the single (at the moment there are 7 albums on ebay as opposed to 19 singles lol), much better quality in terms of colour, the full cover featured instead of the partial cover that's on the single.
Plus it's bigger so you get more vinyl for your money
Again, not a very rare disc, but less common than the single.
Not something i'd expect to see bidders battle for in a fight to the death, there may be one or two bidders and i'd value that disc at about a tenner, and I think you'd get it for as low as a fiver if you were patient and kept your eye open.