A traditional telco will charge about $35/month for unlimited service, not including long distance, and I would bet that this is what 75% of all people have.

For what you're wanting to do, I have no idea where to send you. A million numbers seems like overreaching, though. I also imagine that numbers are allocated dynamically or at least in small blocks, not in huge blocks, but I could be wrong.

Oh, here's something: How to start a Clec