I was thinking back to 2017 or so. I remember prices first got inflated on GTX 1070 and below. We bought a GTX 1080 at my job, and it sold for the normal list price. However, we also bought an AMD RX 580 and that card came at something like a 50% markup, as did GTX 1050 Ti's that we also bought.
The 2021 situation was different, in part because you also had the pandemic fueling demand.
I don't see why the China ban changes much. If Nvidia was able to make enough RTX 4090's to satisfy China's demand before, then they should still be making enough to address it now. If anything, there should be more RTX 4090's for the rest of us, because there's no way China will be able to consume as many at the inflated price they're now having to pay.
IMO, the only thing that's really pushing up demand for RTX 4090's is the ban on H100's and derivative datacenter GPUs. Some of the demand for those GPUs is probably translating into demand for RTX 4090's, instead. But, that would be affecting China's demand for RTX 4090's, regardless of whether the 4090 was itself banned.