Using "Would/Will be" in place of "Is"

[s1m0n]

The example you give there, David, strikes me as being a simple use of the future tense.

English doesn't have a formal grammatic future tense. What we used to have was the subjunctive mood, which lumped the future in with hypothetical statements and other uncertainties. This is what has shifted to modals.

For an example of the subjunctive in use, consider the following:
In UK usage, a headline might say, "the law requires that there is a lifejacket for every passenger." In North American english, "the law requires that there be a lifejacket for every passenger" would be more correct. The latter is the subjunctive, holding on by the skin of its teeth.

[s1m0n]

In "How much for my stuff?" "That will be three dollars, please." I think it is referring to something that has not happened yet - handing over three dollars.

That's certainly true, but there's also an element of softening for the sake of politeness going on, I think. "Will be" seems less aggressive than "is".

[david_h]

Ah now, I take that as being a different proposition entirely

Yes, the "How much for my stuff" was a different proposition from Nano. Not like Using "Would/Will be" in place of "Is" in his other examples.

And yes to s1mon's suggestion about politeness. Sort of a condensed version a cups of tea, talk about the weather, asking after the family etc as a prelude to discussing the price for whatever you have come round to buy.

Less abrupt than to put them through the scanner and read the display. It may even involve looking at the face of the person on the checkout.

[Nanohedron]

Yes, the "How much for my stuff" was a different proposition from Nano.

Aha, but I was the one who cited that example. To me, it's not really all that different.

To make my point, one might (in the States, at least) just as likely hear "That's three dollars" from the cashier. Whatever your personal tastes about the delivery, the overall message remains the same. As s1m0n pointed out, "would/will be" sounds less aggressive; I would go so far as to say more congenial. Earlier I mentioned how it sounds more relaxed to me. The tone is what it's all about; I'm less interested in the rigors of grammar, here.

Less abrupt than to put them through the scanner and read the display. It may even involve looking at the face of the person on the checkout.

I avoid the automated personal checkout. Even though I might have to wait longer, I like cashiers even if they don't like me.

[I.D.10-t]

"Now what's that wailing?"
"And that will be the police."

Fun fact, This was inspired by a failed whaling expedition.

Okay not really.