I've constructed multiple computer systems before and have experience with all three major operating systems and many console operating systems.
Unless you're actually just talking about assembling a PC out of off-the-shelf parts, that's not relevant at all. And if you are, why would anyone care? Maybe some people would like a novelty Saturn-shaped micro-ITX case, but that requires some degree of mechanical design engineering experience. Getting them actually manufactured is its own separate headache.
As I said, I've been sourcing and pricing parts.
That's maybe good for a one-off, not so much for anything beyond that. Components also form only one part of the total cost of a commercial product. Add to that manufacturing, testing, certification, storage, shipping, taxes, etc. etc. Once you have a realistic estimate of what everything will cost, you will need the money to pay for it all.
This all sounds like just daydream fantasy. Which is fine, as long as you realize that's what it is. If you're genuinely interested in electronics design and manufacturing, try to get an industry job and stick your finger in every pie you can.