The RX6700 non-XT could have been had recently for under £300. Looking at the recent Computerbase.de review of the RX6700 non-XT,its about 10% faster than an RX6650XT,so you would have been looking at a 70% improvement in rasterised performance at least:
With the Radeon RX 6650 XT priced at a competitive MSRP of $400, AMD is offering a new contender for the 1080p Value King title. Thanks to an improved 18 Gbps memory subsystem, the RX 6650 XT can extend its performance lead over the NVIDIA RTX 3060.
www.techpowerup.com
Nvidia needs to be reducing the price of their dGPUs,not increasing them. The RTX4080 12GB uses a 104 series type dGPU in terms of size,so it is really an RTX3070 replacement. But it's no point in making "demanding games" if Nvidia overprices these dGPUs,because relatively few will care about buying them at £1000+ when the vast majority of gamers buy much cheaper dGPUs.
In the past mainstream dGPUs had generally decent performance jumps on average,but now they seem to be having a much infrequent set of increases because the top end is jacked up in pricing. Hence companies will look at what the average PC gamer has,and what the consoles use and plan according.
You might get the odd demanding game such as Cyberpunk 2077 or even the upcoming Atomic Heart,but these are not that common and probably require sponsorship.