Meshilicious case: $150 (little extra for the mods)
4 Noctua fans: $125
That means everything without the GPU is $1235. I have no idea what a 4080 costs these days, so if you think $515 is a good price for it, then I'd say it's a good deal.
ETA: Even though AM4 is EoL, a 5800X3D will serve anyone well for probably 6-10 years.
I honestly would contest the price for the ryzen because sure thats how much you pay for a new one but at the same time there are ryzens (am5 sadly) out there that have a lower power consumption, same or better performance at the same price. Another contention would be the hard drives. I would personally never use second hand storage, mostly because i am a paranoid fuck wit, but for me a used drive is at most worth half a new one as soon as someone puts their filthy data on it. But yeah the 4080 is still pretty expensive.
Pretty decent deal for the parts given, though I would also consider if you agree with those parts.
For instance, there might be a killer deal on a 4090, but I wouldn't buy it anyways because I don't want a 4090/I still wouldn't want to pay the discounted price. You should think about whether those parts are parts that you want.
AM4 is somewhat old, but most of the selling price in this case is from the absolutely insane market price of a 4080. Frankly, if I were aiming for that performance tier, I would have gone for a 7900XTX, but Nvidia does have better productivity and ray tracing. Regardless, the 5800X3D holds up very well, even against modern generation halo products. So as long as you're not planning to upgrade the CPU anytime soon, I expect that going AM4 shouldn't be a problem