There's no case on this list, you have a lot of ways to get a free case including the classic "Cardboard Special".

There's no keyboard and mouse, you can get those at the thrift store for like 1$ (They're always at the thrift store, even found an RGB Mech Keyboard for like 5$ once lmao)

Also, like I said, I could def foresee getting my list as-is down to 600 with the right optimizations and sale tracking, right off the bat I can tell you I opted for a 700w PSU when a 400 is really all that would be needed according to the wattage estimate. With a PC you can also buy it piece by piece if needed.

Then you would have 100 to spare for a good case or split between a case and keyboard/mouse if you really want a new KB/Mouse

50 series Nvidia is due for an announcement soon with AMDs offerings prob shortly after so all those nice 30 series are going to go on some good discounts

And this is all new ofc, you could save even more buying used or swapping to the AM4 platform