bus from KLIA to malacca?

Nope, no direct bus from KLIA to Malacca.

You can take a taxi if you want, but I don't think it's cheap...

Another alternative is to take a bus from KLIA to Nilai train station. I can't remember the fare though, I think RM2 is not mistaken. That was 3 years ago.

From Nilai Train Station, take a train to Seremban. From seremban, it's only a few minutes walk to the bus station where you can buy a ticket to Melaka... The whole trip should take about 2 hours, and not more than RM15/person... depending on the frequency of the buses and train...

Recent post on this very subject!

I did the reverse from Malacca to KLIA.

I took an express bus from Malacca to Seremban.
The bus arrived at the "Seremban One" bus terminal.
From "Seremban One", I caught a local bus to KLIA.
The bus is a local bus and stops alot.

If you are going to Malacca from KLIA.
Make your way to the Bus terminal at KLIA located at the lowest floor.
Ask anyone there to point you to the bay where you can catch the bus to Seremban.
The local bus will take you to "Seremban One" bus terminal and from there catch an express bus to Malacca.

Cost? Virtually nothing in terms of USD but make sure you get some local money at the money changers at KLIA before you board the bus.

Good luck.