I bought a Telkomsel SIM for 120,000rp last month - don't have the details to hand - but from a local street seller just after leaving Bali airport my driver knew.
Two weeks later still had 3G and had used it a lot throughout Indonesia, sent lots of texts and made local calls. Was VERY impressed as that equated to about a days 3G if i'd have kept my UK Sim in it.
Also - my phone in the UK is locked to a network - but the Telkomsel Sim had no problems working *
As a result lots of people got to see my dull facebook updates from Komodo and the top of Bromo!
*YMMV