In English, x or time(s) after a number marks a "unit" used by various verbs. A 10x increase. Increase by 10x. Go up 10x. Some of these verbs are negative like decrease or save. "Save 10x" is the same as "divide by 10". Four times less, 5 times smaller etc. are long attested.
No, x literally means multiply. It doesn't somehow also mean divide. They should use the percent sign, it's what it is for. 10x my costs means 10 x mycost, it's literally an equation
It's just inversion, like 2 to the power of 2 or 2 to the power of negative 2. These negative words inverse it just the same. You may dislike it, but millions of people have spoken this way for a long time.
> x literally means multiply
And some use the dot operator or even 2(3) or (2)(3). When programming, we tend to use *.
Thats not how English works.
Saved 10x would imply there was an amount being saved that they multipled.