Im trying to feel the market out to see if there is a need for the following:

A company that can offer a private PBX for $10-$20/month with unlimited extensions and etc along with the ability to offer VoIP service at the following price all on 1 bill:

DID: $1.75/month
Inbound/Outbound Termination: $0.02 per minute ***Discounts available based on volume***
Inbound 800 Termination: $1.75/month + $0.03 per minute

Is there a market for this type of thing?

There are already many pbx providers in this space - Ringcentral, 800PBX, GotVmail to name a few. They are all moving towards unified communications and I think its just another 6 months till we see any player coming up with true unified messaging. Microsoft response point has good integration.

In short - unless you have some unique proposition - expect lot of competition and high churn rate.

There most definately is a market for this yet there are also a few top tier competitors as phonedev said. I feel however that you should not be discouraged by them since all it will do is help to gain marketability for all and increase awareness and market penetration. Specifically with your intentions, that is the norm. Your monthly rate for unlimited calling may be a little on the low side and you might find it hard to keep expenses paid for especially if you consider dedicating a box to each client (which i hope not).