Not exactly. If you assign 80% probability to something, you're still allowed to say that you believe it. It's just an evaluation of your model, I believe.

I certainly read it as "postmodernists notice that the word true is used as mere emphasis ".

Your interpretation doesn't exactly align with the essence of postmodernism (as I see it, I'm no expert).

It makes sense, but I can't entirely convince myself that it's the best way to look at it. A gut feeling that something's wrong - I cannot throw out the time from the equation.

Ad absurdum - I look at everything that I can do with my free time and decide nothing is worth paying $8 per hour. So what do I do? Maybe work, so I can get my $8 back. Yeah, that's the idea.

I'm not convinced that it's the best way to think about it.

I think you're misapplying the method. "Pay $8 to spend an hour on anything" - you're counting the cost twice: one time spending the money, and the second spending the time. Maybe a better metric would be "I'd rather be paid $8 for spending an hour doing exactly nothing".

I may be wrong, though.

It was done by Doyle himself. In 1898 he published two short stories - "The Lost Special" and "The Man with the Watches", where "an amateur reasoner of some celebrity" participates in solving a crime mystery and fails. It was written after Doyle killed off Sherlock, so he is probably parodying the character - he was quite tired with him at the time.