I am not saying that rebadging a component and inflating the price is not disreputable. I am only saying it does not qualify as fraud.
Sticking a super high price on something is not fraud.
As for your diamond tweeter example, I do not know who said what exactly, and I am not a lawyer, so I have no opinion on that, beyond the fact that salespeople are not generally noted for their honesty and integrity. If they were, there would not be such associations with the phrase "used car salesman" that there are.
Basically, people should remember that the interests of the salesperson and your interests are far from identical, and salespeople are motivated to say what is in their best interests, not yours.
As the great philosopher David Hume observed:
We entertain a suspicion concerning any matter of fact, when the witnesses contradict each other; when they are but few, or of a doubtful character; when they have an interest in what they affirm; when they deliver their testimony with hesitation, or on the contrary, with too violent asseverations. There are many other particulars of the same kind, which may diminish or destroy the force of any argument, derived from human testimony.
By "when they have an interest in what they affirm," he means when they have something to gain by saying what they are saying. Salespeople are interested in getting your money, and if what they say forwards that goal, then you have a reason to entertain some suspicion of their veracity. That is because they have a motive to say it that is independent of whether it is true or not.
And you are quite right to point out the fact that sometimes someone says something that is false not because they are trying to deceive you, but because they are themselves deceived. In order for it to be reasonable to believe someone, one should have reason to believe that the person has the relevant knowledge AND
one has reason to believe that they are being honest. Lose either one of those, and you have no reason to believe the person. For the truth of what the person is saying, it makes no difference which it is, though it does make a difference for the person's level of discernment and integrity.