How much would a stock PC with equivalent 3.8 quad, 16 gb of ram, and GTX 1050 graphics card cost?

Nobody measures core count or processor speed anymore because architecture makes the biggest difference. I know of quad core processors like the Core i7-6700 clocked at 3.4ghz that would beat an 8-core FX-9590 clocked at 4.7ghz in nearly every application. So if you went with an AMD FX or A10 CPU then you did yourself no favors. Even AMD's Quad-Core Ryzen 5 1500x is faster than their 8-core FX-8350 CPU.

It would probably be about $500 for that prebuilt if the CPU is an FX-4300 but it's hard to say since we dont know which CPU it is. Beleive it or not, the Pentium g4560 is a better processor despite it being a quad-core. PC builders look up benchmarks to find out how parts perform before choosing a part.

There is also a site called Pcpartpicker.com that has a checklist for rookie builders. Everyone uses that site, even non rookies.

If you are within your return window, I would suggest returning the FX CPU and the AM3 board for something more current.

This is a simple "life" exercise. Go to a site like Newegg and look up the cost of each part you want. Add those costs together. That will tell you what it would cost. That's what I do every time I build one. I don't ask other people what it would cost. I look up the costs myself.