In der Umgangssprache ist es völlig korrekt. Geschäftlich halte ich es für einen Grenzfall, wo es auf den Einzelfall ankommt; im Zweifel immer "a lot more" oder "much more".

It's not exactly wrong, but it's not great grammar - everyone uses it in conversation (in the US at least)
"He spoke way more than I expected"
"We were there way longer than I wanted to be"
"Wow, we're way above the water right now"

I'm not sure if that's exactly the context you remember it from, but that's what I thought of reading your post.

Could someone give a German example/exact translation for this case?

?

viele mehr
= many more (standard)
= a lot more (colloquial)

viel mehr
= much more (standard)
= a lot more (colloquial)

weit mehr
= far more (standard)
= way more (very colloquial, not really standard)

These have similar meanings, but 'way' as an adverb is very colloquial, not really appropriate for writing.

Yes, JLynn, that's what I meant. - It could have been a song or something.

OK, so it's not really wrong but very, very colloquial. - No wonder I can't find it in the dictionary. Thanks, all, for clarifying this.