Thanks Michael! With regards to your questions...

1. The flat-rate is $27/mo per channel. TelAPI also offers channel bursting . This ultimately means developers and businesses have on demand access to additional channels for TelAPI numbers with unlimited inbound calls. E.g. You have 1 unlimited inbound number with 10 channels. Then you receive an 11th call. Channel bursting ensures the call can still access the application and won't ring busy.

2) CallID unmasking allows developers and businesses to identify the number and ID of calls received from 'Blocked' and 'Private' numbers to your TelAPI number

Our parent company TelTech uses it for one of their products: http://www.trapcall.com/