Is there a named fallacy for the argument that a proposition is "believable by comparison"?

Question

Consider an argument where a completely absurd story is presented, and then it is "debunked", and replaced with a more reasonable story. The reasonable story gains credence because it expressly disavows the complete absurdity of the initial story. Also, the listener's capacity for the suspension of disbelief will have been recalibrated by the first story, so that the second story seems relatively tame in comparison. Here is an example:

It has been alleged that I traveled to Mars and back in just one day using a mere paperclip as a rocket. This is utter baloney! How could a paperclip function as a rocket, when it has no fuel?! And how could I go to Mars and back in one day, when it is 75 million kilometers away?! Who would spread such nonsense? The real truth is that I traveled to Mars and back over the course of a year in a conventional spaceship.

This fallacy seems similar to the following things:

1. Raising the price of products in a store so that they can then be put on sale at their original price. People will get the impression that the products are cheaper than they really are, because they will compare them to the list price. This is similar to how the latter story in the fallacy will seem "believable in comparison" to the first story.
2. The fallacy of relative privation, where things are made out to be "not so bad" because others have it worse. Similarly, the latter story in this fallacy is made out to be "not so absurd" in comparison to the first. Maybe this fallacy would be described as "the fallacy of relative absurdity".
3. Compassion fatigue, the psychological condition in which the compassion of a person overexposed to the trauma of others will decline over time. Similarly in this situation, the listener is overexposed to absurdity with the latter story, so they grow somewhat tolerant of it, and learn to withhold their disbelief. When the second story comes, they are so tolerant of absurdity that they automatically withhold their disbelief and do not recognize the absurdity.

Answer 1

Rather than a formal fallacy, this is commonly described as anchoring in cognitive bias.

Answer 2

I would say this is similar to what is sometimes called "argument to moderation". The most common cases of this take the form of arguing that some position is plausible because it lies between two others that are more extreme. It appeals to our willingness to seek a compromise in order to resolve a disputed claim, but it is not of itself a cogent argument that one of the extremes is false. In your example, one might gloss the argument as saying maybe I didn't go to Mars, or maybe I went there riding on a paperclip, so let's compromise and say I went in a spaceship.

Answer 3

I'm not sure what the name of the fallacy is but as I suggested in my comment that's not very important. What you're describing is in the family of "non-sequitur" or "red herring" fallacies.

Formalized, they have the structure:

1. A
2. B ... Ergo, Q.

(where Q does not appear in the argument).

The psychological feature might overlap with some aspects of philosophy and be looked at in "experimental philosophy" but I would say it's no longer then primarily about "fallacies" but fallacy as used in philosophy means an error in the reasoning of an argument. Ergo, if there is no argument, there can be no fallacy.