Football fans complained to BBC Radio 5 live that flights around that date cost £1,000 instead of £250 normally.
But Mr Lundgren said the price was higher than average because there had been an "enormous" surge in demand.
"That is actually how the system works," he said.
Mr Lundgren said 42 million people had flown with the airline over the winter season, with 65% of them paying £50 or less.
"The whole pricing picture is very dynamic," he said, adding that at peak booking times, EasyJet could fill a plane in six seconds.
"That's how quickly this goes and this is how the system reacts."
Mr Lundgren added: "I can understand if people think that the prices are high on this occasion, because it is higher than the average.
"But there's no doubt that this was an occasion where the prices went very high because the demand was enormous."
He maintained that in comparison with other airlines, EasyJet was still offering lower prices, despite the huge increase.
His comments came after EasyJet reported a loss of £275m in the six months to the end of March, compared with a £68m loss in the same period a year earlier.
The airline said cost per seat had gone up 3.9% due to fuel price increases and the impact of currency movements, while revenue per seat had fallen by 6.3% to £50.71.
Easyjet also said had it suffered from "the impact of drones at Gatwick in December", which it said had cost it £10m.
In April, EasyJet had warned about "weak" summer sales amid Brexit uncertainty.
In its latest results, the carrier said revenue per seat in the second half of the year would be slightly lower.
"This is not helped by the ongoing negative impact of Brexit-related market uncertainty as well as a wider macroeconomic slowdown in Europe," it said.