I have no idea how you worked that one out
The cheapest 3090 costs around £450 more then the cheapest 2080ti was on release
If you watched the video above you would have seen the real price was $1200 in USA and in UK they were £1200, yes they had a few at under but that lasted what 5 days ? Then most AIBs were £1200. Also the 3090 is a better deal, especially for work related uses, it is over double the performance for some work related use (check review below). In games it is 50% faster than a 2080ti. Not everyone buys these cards for gaming only.
Dual NVIDIA GeForce RTX 3090 NVLink Performance Review
https://www.servethehome.com/dual-nvidia-geforce-rtx-3090-nvlink-performance-review-asus-zotac/