Add 103 up to 685.
IP phones register to CM. You can have 30000 on a CM with 1 G430. They won't all get dial tone at the same time. If you have SIP trunks and they're all shuffling, direct audio, no transcoding 711/729, then you can have those 30000 phones on 30000 SIP trunks not using any DSPs.
It's all a matter of what kind of traffic you're planning to handle.