three times as much / more than

They both convey the same basic meaning, and both would be used by native speakers.

The second one sounds more simple.

The one that better expressed the meaning/nuance that fit a particular situation.

This could be twice as much fun then some.

I like what's behind 1.

I was rather hoping for the usual 200 post squabble on this one.

When"as much as" equals "more than" the phrases will mean the same despite the intention to convey equivalence that the second (incorrect lol) sentence attempts to connote.

I'd say number one, although it has more to do with logic than being a native speaker. Nine dollars is not three times more than three dollars. Nine dollars is six dollars more than three dollars, and six dollars is only two times as much as three dollars. So, in fact, nine dollars is three times more than three dollars is an illogical statement.