Hobay, the equation is not so simple.
Whilst the direct flight may offer cost savings to Virgin they still need to fill the aircraft to take advantage of that cost saving. In the past they have reasoned that they can not fill a 737 so the route has not been active but they must think now they have a good chance of filling the e-jet.
A knock on effect is that effective load factors on the service from HBA-MEL and MEL-CBR will drop as a result of reduced connecting pax. These passengers helped increase load factors and supplemented income on the routes. Definately
VB must be hoping to take some QF/J* & tiger pax who would have to connect through Melbourne on possibly cheaper fares.