How much is this old beast worth nowadays?

Currently have an old PC which I built all the way back in late 2013 I believe. It's served me really well but now starting to show its age and I'm trying to upgrade to something more modern and power efficient before it completely die. 

Specs:
CPU: AMD FX8350 @ stock 4GHz (never OC'd that damn thing).
RAM: 2 x 4GB @ 1600 (8GB was surprisingly spacious back in the days).
Mobo: Gigabyte 990X Gaming SLI (which I never got to SLI). 
GPU: GTX Titan OG (a silly move which I immediately regret as I play with 60FPS w/ vsync).
PSU: Corsair 650 something. The budget model that I grabbed for around $80.
Case: Antec 1200. 

I think I blew-up an entire bonus of $3,500 on that freaking thing and as you can tell, it's not a very budget efficient build. I was only 23. A young, naïve and cocky guy who landed a great job and became too successful too soon for his own good and this PC was sort of a pat on my back. An 'atta boy', if you will. 

Anyhow, I'm trying to get rid of this thing and build something more down to Earth as I don't even have a job at the moment! 

I've set my eyes on an i5-10400F, 8GB of DDR4 RAM (I never actually got the chance to fill-up my current 8GB RAM so), a cheap albeit decent mid tower chassis (nothing extravagant) and maybe an RTX3060 (whenever they become available). I won't be salvaging any parts from my current rig as I want to sell it as is.

Sorry about the rant! I'm old, lonely and kinda bitter!