As much as we'd like there to be a direct bus from Subang Airport to Larkin Sentral, so far, unfortunately, no bus operator has started one. In view of this, the only real way to travel between Subang Airport and Larkin Sentral is by taxi. It's quite a drive though, at 4 hours and possible above.
Of course the good news is that traveling by taxi in Malaysia isn't even close to the cost of taxi rates in the west. Add to this the low Ringgit and actually taking the cab is quite the deal, especially considering the awesome landscapes you'll be crossing along the way. Not to mention the fun stops you'll be able to make for a local meal or some yummie traditional Malay-style munchies.
By the way, if you still need to book your flight, have a look at the real-time airline platform below. There's some good promos on offer.