The figure of 1.98 billion is the operational budget, said RTS in its Infrarouge programme on Wednesday, but does not account for the cost of bidding, infrastructure costs nor the bill for security during the Games.
The total would be 2.4 billion, the financial director of the Sion 2026 committee told the broadcaster.
Speaking to RTS, the committee's vice-president Bernard Rüeger acknowledged failings in communication over the budget and vowed to be “more transparent” in future.
The cost of building an Olympic village is not included in the budget either, he said, but that would be financed by a private company and rented out to Games organizers.
Security during the Games would cost 300 million francs, with an estimated 2,500 police officers per day needed over a three month period, according to a feasibility report seen by RTS.
And the security bill is likely to increase, said the report, as it did during the Vancouver Games.
Valais minister Frédéric Favre has said he hopes other cantons would offer financial help to Valais to meet the costs of security.
The Swiss government last week pledged just under a billion francs in support of Sion 2026, raising the chances the Valais city will bid.
However plans could be scuppered entirely if residents of the canton vote against it in a planned referendum in June 2018.
Referendums may also be required in the neighbouring cantons of Bern, Friboug and Vaud which would host certain events during the Games under current plans.
Voters in the canton of Graubünden in February rejected the idea of a separate bid to host the Games there.
The International Olympic Committee in Lausanne will be hoping that Valais residents back the project so Sion's bid can go ahead, since voters in Austria's Tyrol region recently quashed the idea of bidding for the Games themselves, leaving only Sion and Calgary in Canada still considering a bid.