[Closed] Thinking of selling my Swift for a plus...

Please delete if not allowed.....
Tempted to sell my Mk1 Singular Swift in large running an 8 speed alfine which has only covered about 100 miles since purchased 6 month ago, running XT brakes and 120mm Recon solo airs with on-one reet'ard rims, the frame has some knocks but is about 6 years old now.
Now I love it to death, and it has served me well, I just fancy a plus bike and this would need to go but I don't know how much to ask for it, would someone be able to advise?
Some say 40% of purchase price, but that would put it about £700?

I'm looking at a 2016 beast of the east 1 demo bike for £1600 been out 3 times...

Thanks in advance