400 is supposed to include everything for MAS. I think they are supposed to list it that way.

And 165x2 = 330 is NOT everything. Last time Australia sued Air Asia for not listing the actual price and alot of hidden charges.
This.

But i think most major airlines plants Cookie in your browser. Everything u recheck the price, it will increase. So always clear your cookies, use different browser, or maybe "incognito mode" for chrome. Im not sure MAS' website got tracker or not. Just to be safe.

It makes no sense to travel by air to singapore if you live Klang Valley. It'll take you 45 minutes to an hour to reach the airport, an hour to check in and board, 50 minutes flight (not including taxiing, landing, unboarding, collecting your luggage), and another 20 minutes getting from airport to city center.

You're looking at about 4 hours of commute time.

By bus, just add an extra hour at a half of the cost, and you can sleep for 75% of the journey.

Peak season you also suffer high air fare prices, and long queues at airports. Try sleeping when you're waiting to board