FreePBX is free both in terms of price and in terms of freedom.
However, there are obviously costs associated with setting up any system, from the cost of the server hardware (or vm), the phone cost, etc. It’s also important that you factor in the soft costs of the effort needed to setup and maintain a system. The more hands-on you are, the less you have to pay someone else to provide this effort.
You can absolutely setup a new system on your own hardware (or your own VM) and consult the forum here for help or pay Sangoma Support to assist with configuration when you get stuck. On the other end of the scale is purchasing a new server with an Up-And-Running package and have Sangoma Support setup the entire system to your specs.
Sounds like there is a comm breakdown with your sales rep. If you’re not interested in Switchvox (which is a great system too), just say so and get them pointed toward FreePBX.