Cronulla chief executive Tony Zappia says the NRL will never stop players leaving Australia if they continue to attract offers of $1 million a season overseas.

Zappia said the NRL could not compete with the riches on offer in Europe, such as the reported $1.5 million a season reportedly being offered to Sonny Bill Williams to switch codes and play rugby union with Toulon.

"There'll always be players moving overseas, whether it be rugby union or the UK Super League," Zappia said.

"I don't think we're ever going to stop it.

"We need to understand the market in Australia is different to a market overseas whether it be in France or the UK, where there's much bigger corporate support and pay television is much bigger because of the population differences to Australia."

The most any NRL player could hope to earn from a playing contract is in the vicinity of $500,000 a season.

Despite the salaries reportedly on offer in France, Zappia said he had his doubts over their validity.

"Let's wait and see if all these players get paid their money," Zappia said of those making the exodus to French rugby.

"There's been instances in the past where players have gone to play rugby league or rugby union in France where they haven't been paid 100 per cent of their money, so let's just wait and see whether they actually get all the money that's been talked about."

South Sydney chief executive Shane Richardson said French clubs would not necessarily keep offering the big dollars year after year.

"There's people in France with millions of dollars but one thing I've learnt about millionaires is that they don't like losing money," Richardson said.

"I don't see how they can justify the money they pay these guys in any way, shape or form.

"I've been there myself and I spoke this morning to a Super League mate this morning and they're sitting there waiting and watching because it's got ramifications for league in England as well."

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