No.

1 usd = 63.9 Rp as of today.

I btc @ 4909 usd = 313685.1 Rp.

Thats ok, I see you meant to use Indonesian Rupee which is called IDR on exchanges.

So in IDR 1 btc @ 4909 is 65000000 IDR. That makes sense. But I have to question the claim of 6000000 IDR mined in a month on a single pc.

To reach that amount of BTC, if you are only mining BTC, you will need at least 500 Gh/s or half a Terahash!

That is well above what any video card setup's on a normal pc, even a high end gaming pc can do. So either he's got quite a rig set up, or he's already using specialized mining hardware. Where I am from, it would cost me about $2000 USD to get ~500 Gh/s of btc mining power. That would still take up to 6 months to just pay for itself. How is your friend claiming to pull almost 500 bux USD in mining from a normal PC?