The 30$ phones are based on the Spreadtrum SC6821 chipset and are sold around Asia. There are four different ones in India alone (Intex Cloud Fx f.e.) that go for this price.

Probably can get some SC6820 phones as well and make a port. Don't know if those are readily available in western countries.

Its though to get your hands on the super cheap handsets in US / Europe. But if there's sufficient interest we can go to an odm and just order 20,000 for <25$.

Edit: the cherry mobile phone went for 23$(!!) During their intro offering