Really? The graphics card sold for less than it cost new, and the point I should take away from that is that 'I threw away the £ difference'. Your ability to quantify subjective value is astounding.
I could buy a new Vega 56 with the money left over from the GPU sale + RX 550, so in pure GPU power terms the money I've thrown away is only the difference between a Vega 56 + RX 550 vs 1070 Ti, plus fully working FreeSync in all screen modes that the nVidia card couldn't deliver - difficult one to quantify.
And then there's the other dimension of time - I'm not playing triple A games right now so the 1070 Ti would just be depreciating in value, plus I decided it wasn't quite fit for purpose anyway and would ideally need to be upgraded sooner rather than later, etc. Complicated factors.