I don't think the 3900x is really necessary; could cut that processor price in half and get a 3600. Could also reduce the cooler to a Hyper 212 or Noctua, probably not a good idea to overclock the 3600 long term past what those coolers can take anyway.
Cases are personal preference, but I love my Meshify C, and it's significantly cheaper than what you have listed.
An x570 board is only really necessary if you care about the PCIe 4.0. x470 boards are almost half the price. I like the x470 Taichi from ASRock.
The 2080s could be reduced to a 2070s, but it would probably be a noticeable drop in performance.
Beyond that, it's more pennies you're picking up. You could find cheaper fans (Arctic P12s come to mind), and you could reduce the NVMe size and get a larger hard drive for long term storage.