Do not get your hopes up for a good $/performance ratio. A lot of people saying 4xxx is so much more powerful than 3xxx. If that were true, the 3090TI would not be outperforming the 4080 in some games. Also, Nvidia's claims of 4x the performance only applies to games running DLSS 3, games without DLSS 3 will not see a huge performance increase when going from RTX 3xxx to RTX 4xxx.
Although DLSS 3 will be exclusive to the upcoming NVIDIA GeForce RTX 4000 series, it might become compatible with the RTX 2000 and 3000 series in the future. However, if this happens, those older cards won't get the same benefits as the RTX 4000 (or later) when running DLSS 3-enabled games.