Representing Tonga can be an expensive business.
Martens is proud to represent Tonga
Scrum-half Sililo Martens often has to fork out as much as £1,000 for the privilege of representing his country.
The Tongan Rugby Football Union are among those bodies strapped for cash and struggle to pay the air fares for their players scattered across the world.
But Martens says the lure of representing his country, as well as a little family fear, are enough for him to dig deep.
He told the BBC Sport website: "It's frustrating but it keeps a smile on my mum's face and it's always important to keep my mum happy.
"But it shows we're not there for the money. We're there for the pride of pulling on the Tongan jersey."
That pride has proved insufficient to lure a lot of big names to represent their nationality. The Tongan-born Jonah Lomu famously opted for the All Blacks jersey instead, while the Kefu brothers have represented Australia despite their Tongan roots.
In contrast, Martens was brought up in New Zealand but opted to represent his mother's country.
He explained: "I had played New Zealand schools but was then approached to play for Tonga. We're full of scrum-halves in New Zealand so there would have been a long queue.
"Growing up as kid in New Zealand, it was a dream to play for the All Blacks. But I'm half Tongan and when I first slipped on the jersey I was as happy and proud to slip that on as I was the New Zealand jersey."
Martens has since grown in stature as one of Tonga's more established internationals.
He plays for the Warriors in Wales, an amalgamation of Pontypridd and Bridgend, and has been hailed by national coach Jim Love as being "as good as any scrum-half in New Zealand".
Under Love, Tonga have increasingly built on their strengths - the sheer physicality of their game - by focusing on more technical, defence-minded aspects of their play.
"Jim Love is well respected and specialises in our defence. We've always been good at big hits but we fly out without organisation and miss tackles.
"Jim has taught us line defence as well as focusing more heavily on fitness - another weak spot historically for us Tongans."
Martens believes Love's expertise can help the team book a place in the quarter-finals, building on their win against Italy last time around as well as an impressive display against the All Blacks.
Once again both New Zealand and the Azzurri will be pool opponents and the All Blacks clash will be the "main event, the real honour" according to the Kiwi-born Martens.
But a lot will go on behind the scenes before kick-off in their opening game against Italy on 15 October.
The players from the "friendly islands", as Tonga is known, pride themselves on their religious beliefs and, in particular prayer.
A preacher will be part of the squad that travels to Australia, as is the case on any tour. And his job will be to lead daily prayers as well as a final prayer before each game.
"We're not bible bashers, but we all believe in the Lord," added Martens. "It's what our parents and ancestors have always done."
Once out on the field a different side to their make-up appears in the sipi tau - their haka-style pre-match war dance.
While Martens admits the irony of the "friendly islanders" performing a war dance is not lost on the players, the ritual remains an important part of the game.
"It's basically about holding our flag up high and saying we're going to challenge you to war," he said.
Whatever the cost, Martens will be happy to pay it.