So let's see
RTX 3090 5248 CUDA, 1695 MHz boost, 24 GB, 936 GB/s, 350 W, 7 nm process
RTX 2080 Ti 4352 CUDA, 1545 MHz boost, 11 GB, 616 GB/s, 250 W, 12 nm process
I guess all the potential fab process power savings were erased by the extra RAM, RAM speed, CUDA, RT and tensor cores.
Edit: Maybe comparing to the RTX 3080 is more informative:
RTX 3080 4352 CUDA, 1710 MHz boost, 10 GB, 760 GB/s, 320 W, 7 nm process
RTX 2080 Ti 4352 CUDA, 1545 MHz boost, 11 GB, 616 GB/s, 250 W, 12 nm process
Almost no difference between these cards except on the RT and Tensor side. If the price is much lower than $1000 for the 3080 then you can get 2080 Ti performance on the 'cheap'.