So Far:
Copper
Silver
Gold
As everyone knows, 100 Copper = 1 Silver and 100 Silver = 1 Gold.
Shouldn’t we add another exchange, maybe Platinum and Gems.
100 Gold = 1 Platinum
100 Platinum = 1 Gem
To help crunch numbers in the AH and make it easier to read. Maybe get rid of Copper?
So you want to make mailing more expensive by raising its cost by 70 non existent copper to 1 silver?
Copper
Silver
Gold
Platinum
Gem
This is now 5 currencies, up from 3. If we remove copper, we’re now at 4 currencies, up from 3. If we remove copper and have just silver and gold, would require rebalancing drops and vendor prices at early levels, something they don’t need to waste time on. Edit; Possibly could cause a ripple effect into higher levels as well.
This suggestion pops up from time, and I don’t understand why. Are we scared of XXG.XXS.XXC numbers? Why does the economy need a reshuffle by messing with currencies?
I feel they could, but there’s not much gain to do so. What we got already works.
But why? What does this actually accomplish?
So you’re scared of large numbers, gotcha.
Wdym? AH is already easy to read.
Adding 1 or 2 more currencies would not benefit the AH or currency exchange at all. Keep it simple as it is, no need to reinvent the wheel here. It’s been easy to read and figure out with our Giga Gaming Brains how to work the AH and to choose the cheapest price value of that item for nearly 16 years. Why add MORE confusion and values to the AH? There’s no need, plain and simple.
Didn’t they already remove copper from the auction house? Seems like OP is brainstorming solutions for a problem that doesn’t exist.
If this is your goal 
I wonder if addons could do it for you.
I have been in support of adding new currencies for a long time. Mostly because this is essentially a wipe of currency if it was done right. Something that has been needed sense around WoD. And people couldn’t even be mad about it, because it’s not a real wipe.
Not entirely true, read the above. That is a gain imho. I’m sure others would disagree though.
What’s easier to read
100000
or
100
I don’t feel there’s any substancial gain from doing it still. 
If the gold cap is the same, nothing has changed.
This defiantly falls under the category of “if it is not broke don’t fix it.” That has been done enough in the game already.
I hope they add a currency conversion for coalescing visions. I have have over 700,000 on multiple characters and even at the worst exchange rate, there has to be some money there.
1 copper per 100,000
Not sure if you noticed but commas are used to make numbers easier to read in the game. So that 100000 is written as 100,000 which is just as easy to read as 100.
So, what’s your point again?
100,000 isn’t as easy to read as 100
more text = more difficulty
How much more? Not much, but to say none? Dishonest
Accidentally give a guy 100 gems (1m gold) for signing my bank charter. He still asks “is that it”. I hate this game.
Actually, Europeans, being on the back side of the Earth, use their commas and periods backwards compared to us sensible Left-Pondians. So, they’d write your number as 1.500,25. Quite confusing! This is why certain publications advocate for using spaces to separate the large number groups and periods for the decimal (1 500.25).
What you need is an addon that adds large number separators. To automatically fix
so you can stop worrying about them.