[rfiat]

> For the opposite word, "expensive", it all depends on the word before it: "as expensive" or "more expensive".

Frustratingly, I find this isn't always true in practice. Lots of people use "x times as y" and "x times more y" interchangeably. To avoid ambiguity I try to only use the former in any context where precision is useful.

[noja]

True. But people also say "percentage" when they mean "percentage points". Once they notice the difference they tend to stay right.