Airvasia, lion air, sriwijaya, citi link all cheapish, but you need to be lucky. Air asia is cheaper if you book way in advance or they have a sale but tickets cannot be changed and they charge for pretty much everything. Lion can have low prices but are often late. Sriwijaya are good but limited in flight times depending where you want to go. Citi link are good but limited and are owned by Garuda. There is a new kid on the block, batik air which is owned by Lion but don't know much about them.
Follow Air asia on twitter and they will tell you when the sales are. I have flown to Bali with them for 200k one way so there are deals to be had.
Air Asia is pretty decent and probably the cheapest. When you book online that is. They often have promotions and would go very very low (after tax). Though you have to pay other things like luggage etc(but why should you when all you need is a backpack/small hand carry luggage?) Go to their website and create an account, you'd get newsletter every now and then with informations regarding low fares, promotions,new routes and even free seats.
oh okie thanks guys! i was actually looking at those search travel sites like wego indonesiato buy my tickets instead of the airline itself. Cos I am lazy to check each site for the latest updates each time so I like these kind of services that do the work for me. hehe. I did hear that Lion Air is pretty good though.
@princess sandra, for a moment i read too quickly and thought you wrote sushi air. lol!