Organisers had said in December that more than eight million pounds ($10.08 million) would be offered with the meeting hosting million pound races for the first time.
On Thursday they announced amended prize money of 3.68 million pounds.
Ascot Racecourse chief executive Guy Henderson said in a statement that 2020 had been set to be a landmark year before the "unprecedented times".
"Some 70% of our annual income comes from public admissions, including hospitality," he said.
The eight Group One races will each be run for 250,000 pounds. ($1 = 0.7935 pounds) (Reporting by Alan Baldwin, editing by Pritha Sarkar)