The Updox people are fine with this.
Your 2000+ faxes each month would still be covered by your base monthly rate.
I don't see how this is possible unless you have a dedicated fax line. Faxes come in on a regular phone line, then it imports these faxes that come in on a regular phone line and then are uploaded into Updox. In this case, UpDox is essentially a management interface, right?
I had setup a routing rule that sent all faxes to the staff email, but they preferred having it in a folder.