There is a small-group Beginner Class starting the first Monday of every month at Cinta Bahasa, and the cost is around 3.500.000 for 40 hours, which is good. The maximum is 6 students, but in my group there was only 4. The teacher was absolutely fantastic.
We started the course speaking to each other in English, and by halfway we were only speaking Indonesian. That was cool because there was a Japanese student and a Russian student and their English was not so good.
Now we are friends, but we only speak Bahasa Indonesia to each other. I think that's funny, that Indonesian and not English is our shared language.