Air Niugini flights

I have looked at flights in and out of Vanimo and I see if it is round trip I would save about 40-60€, rather than one way. The options are flying Vanimo-Madang or Vanimo-Wewak? Is it easy to get back and forth between Madang and Wewak? What are my options and how long does it take and is ground transport going to cost me the difference of flights, about 40€? If so I will go back to option one which would be fly Vanimo-Madang and Wewak-Vanimo.

Thanks again.

Ground transport from Vanimo to Wewak means waiting around either for a direct ship or a banana boat to Aitepe, then a PMV to Wewak there.
While waiting, you'd probably spend more money than that 40€, not to mention the time wasted - neither Vanimo nor Aitepe are wildly exciting.