Spark have yet to release all the coverage details, but the RWC app will be available to non-Spark customers. Fans will be able to buy individual games.
Saarinen said the pricing also represented another blow to Sky TV.
"Of course you have to consider what would someone who is not so well off think about the $100," he said.
"But I believe that today it is not a lot of money for people. Around $100 is really attractive and I also think it will deter the pirates.
"There are always ways of getting around things and people willing to do it, as we saw with the boxing. But when they made things like downloading music cheap on the internet no one bothered to pirate anymore."
On the ability of the networks to meet the RWC internet demand, Saarinen said: "They will make sure it works — people will go mental if there are any problems.
"If problems did happen, someone would have to resign. New Zealand would not forgive that."
He said New Zealand had kept pace with technology advances, whereas Australia was striking problems because it upgraded older technology.
But he suspects homes on the old ADSL network, and or with old routers, could strike problems if too many devices were being used at one time. Those customers would be advised to upgrade, to VDSL or fibre.
RWC watchers might also have to upgrade their internet speed and data caps or risk having their speed slowed down and big bills. It has yet to be revealed if RWC viewing would count against Spark customers' data cap, and what the data cap terms would be for non-Spark customers using the RWC app.
As for Sky, Saarinen said the tide continued to turn against the giant sports provider, which has tried to stem the flow of departing customers with a new subscription package.
"I think this is a great move by Spark and it will mean money staying in this country...TVNZ should have looked at something like this a couple of years ago," he said.
"Sky have got to maintain a satellite network and structures on the land. Spark can simply use an existing network. Sky basically looks dead in the water to me.
"For the World Cup, you pay around $100 with no further long term commitment. It is all simple and nice."