The acquisition of Sky by Rupert Murdoch’s 21st Century Fox is costing the media mogul about $2.5bn (£2bn) less than it would have before the Brexit vote that was backed by the majority of the tycoon’s newspapers.

The plunge in the value of sterling over the last six months means the US company is paying about 15% less than it would have done if the deal was struck on the day of the referendum on 23 June.

Fox and Sky announced on Friday they had agreed a deal for Murdoch’s film and television firm to pay £11.2bn for the 61% of Sky it does not already own, equivalent to $14.1bn.

However, since the vote sterling has fallen from about $1.48 to under $1.26, meaning if Fox had made the same £10.75 per share offer on the day of the referendum, it would have cost in the region of $16.6bn – close to $2.5bn more.

Murdoch’s papers the Sun and the Sunday Times both backed Brexit, but the Times ran a leader supporting remain. Murdoch himself described the vote for Brexit as “wonderful” just days after the referendum.

The newspapers were separated from Fox in 2013 and are owned through Murdoch’s subsidiary News Corp.

Last week Enders Analysis analyst Claire Enders told the Guardian that Murdoch’s son James, who is chief executive of Fox, was making a bet on Sky’s future success after sterling “dropped like a stone”.

She added: “James Murdoch is saying ‘I believe in this company and you don’t’ – it’s pure arbitrage.”