Trying to make the math easy, if official parts cost $80 to produce due to licensing or whatever, and are sold for $100, is it necessarily a scam if you can produce functionally similar parts without the licensing concerns for, say, $10, but charge $90 for them?

Huge profit margin, but you're able to produce much more cheaply than a competitor. Some would say you earned that margin, and in a fair and open market if someone else can also produce them for $10 you'll see prices start falling quickly. If they can't, I don't see how it's a "scam" for you to make money in that scenario.