The NSW government's plan to phase out a range of paper tickets could mean some Illawarra commuters on quarterly tickets will pay $110 more to travel to and from Sydney.
But Transport Minister Gladys Berejiklian said comparisons between paper tickets and the new Opal system were not "accurate".
Ms Berejiklian said on Sunday that 14 paper tickets types would be "retired" on September 1.
Ms Berejiklian said retiring old paper tickets would allow the NSW government to continue to modernise the transport network.
"Since the start of the Opal roll-out 18 months ago we have said that the timing of the retirement of paper tickets would be dependent on how many customers are using the system, and so far we are very happy with the popularity of Opal," Ms Berejiklian said.
Among the ticket types being phased out are adult weekly, fortnightly, monthly, quarterly and yearly tickets.
All these tickets can be purchased right up to September 1 and can be used until they expire.
It's part of a move to increase the usage of the Opal system - the government said 280,000 cards had already been issued.
For a commuter travelling from Wollongong to Central stations each day for work, the Opal card will end up slightly cheaper than the weekly or fortnightly paper tickets - $1 and $2.
However, those using monthly and quarterly tickets will end up paying more to use the Opal card - $18 and $110 respectively.
Ms Berejiklian said making comparisons between the price of paper tickets and Opal was "not accurate" because Opal's cost was "tailored to an individual's travel".
She said monthly and quarterly tickets made up only a small amount of ticket sales.
"Few people can afford to pay the large upfront payments for periodicals and that is why they represent less than 1 per cent of all train tickets sold across the network," Ms Berejiklian said.
She said Opal cards will soon be available at retail stores and "pop-up kiosks" on train stations.