Q:

"Ridiculous amount": semantic change (amelioration) originated from an antiphrasis? When and how?

"Ridiculous" means laughable, laughable because it is obviously and hilariously not good enough.
However in English "a ridiculous amount of money" is "a ridiculously large amount of money". In general it seems that "a ridiculous amount" is always "a ridiculously large amount":

«That's an absolutely ridiculous price for that sweater»
«Don't be ridiculous! You can't pay £50 for a T-shirt!» «They ate and drank a ridiculous amount» «The meal was ridiculously expensive»
«Hedge fund giant David Tepper made a ridiculous amount of money in 2013»
«Beyoncé has sold a ridiculous amount of albums since Friday»
«GTA role offered to Alec Baldwin for “a ridiculous amount of money”. Alec Baldwin turned down an “incomprehensible amount” of money»
«… it's a ridiculous amount of pain for such a light touch …»
«5 year old genius knows a ridiculous amount of geography, turns down a Sony tablet»
«Our teacher gave us a ridiculous amount of homework tonight», nº 24
«She had spent a ridiculous amount of money buying this apartment, free and clear, for cash, the way other people bought sweaters. She had spent a ridiculous amount of money buying her little tangerine orange Mercedes sports car, also for cash»
«I did love that piece, Bernard, but you were right when you said that $1,688,000 was a ridiculous amount of money to pay for a piece of furniture. So I decided to auction it off in the hope of obtaining an equally ridiculous amount of money that I could use for a better purpose», page 199

In my opinion this is an antiphrasis exactly as "terrific", "tremendous", "awful", "sick", "bad", "wicked", etc., when used with a positive connotation.
When an antiphrasis becomes popular, a proper semantic change occurs, in these cases it would be called an amelioration. But it is important to stress how a semantic change of this type is often originated from an antiphrasis.
If you agree with this premise, my question is: when and how was the meaning of the adjective "ridiculous" inverted from "obviously and hilariously not good" to "absurdly great" when referred to an amount of money?
Otherwise, can you explain why you do not agree with the premise?

A:

I'd suspect that this is not so much amelioration as a broadening, so a 'ridiculous amount of money' is a comment on the situation rather than on the amount of money being referred to per se. It would be unusual to speak of there being a 'ridiculous amount of money' in say Fort Knox. It would be more usual to speak of a 'ridiculous amount of money' being taken from taxes to enable a sporting event, or spending a 'ridiculous amount of money' on hair products, or sellers of 'Big Issue' making a 'ridiculous amount of money'. 'Ridiculous' or 'ridiculously' in 'ridiculously large' are comments on the decisions, or situations judged crazy, rather than merely the largeness of the wad of banknotes. So AHD's definition

ridiculous: adj. Deserving or inspiring ridicule; absurd,
  preposterous, or silly.

still applies, though at a distance.
Of the following synonyms given at your reference, only some have made the leap to being regularly used to comment on the situation while appearing to modify a noun specifying only part of that situation (eg absurd, ludicrous): 

cockamamy (or cockamamie), comical, derisive, derisory, farcical,
  laughable,  pathetic, preposterous, risible, silly //Related Words
  asinine, brainless, dumb, fatuous, foolish, half-baked, half-witted,
  harebrained, idiotic (also idiotical), imbecile (or imbecilic), inane,
  jerky, moronic, nonsensical, simpleminded, stupid, unwise,
  weak-minded, witless; balmy, cockeyed, crazy, cuckoo, daffy, daft,
  dotty, insane, kooky (also kookie), loony (also looney), lunatic, mad,
  nutty, screwball, senseless, wacky (also whacky); fantastic (also
  fantastical), far-fetched, inconceivable, incredible, unbelievable,
  unreal, unrealistic, unreasonable; illogical, irrational

A:

To answer the question of drift of meaning, you need a historical dictionary, like OED. I'm not going to reproduce the whole entry.

ridiculous
A. adj
1.
a. Arousing or deserving mockery or derision; absurd, preposterous; risible.

α.
    1533   T. Elyot Of Knowl. Wise Man ii. 41   Horrible, monstrouse, and in some fact ridiculouse: that is to say, to be laughed at.
β.
    1575   G. Gascoigne Glasse of Gouernem. iv. vii. sig. I. ivv,   They haue not shamed, by a vaine shew of learning to defend such propositions, as seeme most rediculous & estranged from reason.

b. Eng. regional and U.S. regional (south. and south Midland). Outrageous, scandalous; indecent. Now rare.

1839   G. C. Lewis Gloss. Words Herefordshire 87   Ridiculous, scandalous, morally wrong.

c. orig. Jazz slang. Outstanding, excellent; unbelievably good. Cf. crazy adj. 4d.

1959  Jazz Summer 209   His technique is ridiculous!

1c [“outstanding, excellent”] is obviously an example of antiphrasis, and is four hundred years later than the word’s first appearance in English. 
However, 1b [“outrageous, indecent”] is only a short step from “preposterous” but that’s the meaning which would fit “a ridiculous amount of money”. I don’t believe that’s antiphrasis: it’s a shift in meaning, not a complete reversal. (And I think I might dispute the rare tag.)

