Toll calculator is at https://www.ezdrivema.com/TollCalculator and will show the differences between ma transponder, oos transponder, and no transponder.

My understanding from WBUR is that there is a 6 month grace window for those with no transponder.

For what it is worth, I had a NY transponder from back when it was FastLane and Citizens Bank took an extra leg just for you to -have- a transponder, forget the usage billing. The MA ezpass website was a bust for me to get MA transponders, but it was only a moment of work at the EZ Pass physical location.