Let's look at this logically then.
If you're releasing a 980 perf card at £150, what's coming in above that? A 980ti is 30% more powerful, so let's assume we can charge about 50% more. £225.
And your best mid-sized card (of the ones coming in 2016) is probably 980ti+30%. So what can we charge for that? Let's add another 50% to the price... giving us £340 for the top end card this year.
So (my estimation of) your predictions would be:
~980 perf: £150
~980ti perf: £225
~980ti x1.3 £340
Does that about cover it?
To me I look at that list and think the first two cards are /way/ under-priced. I'd absolutely love it to be true, and I'd bite the hand off the company prepared to give me 980ti perf for £225.