Business leaders say the Olympic torch relay last month injected up to £20 million extra into the Devon and Cornwall economy.
The historic flame began its journey to the Games in London at Land's End and is still snaking its way to its final destination.
A new report by council chiefs in Cornwall published on Friday showed almost 200,000 spectators – 35 per cent of the population of Cornwall – came out to cheer to torch.
The burst of Olympic enthusiasm is said to have generated a potential £3.77 million boost to the local economy.
However, business leaders described the estimate as "conservative".
They said the actual figure injected into the economy could be at least double.
Tim Jones, the chairman at Devon and Cornwall Business Council said the event was "phenomenal" for both counties.
He said: "I think the council's estimate is on the conservative side – you can at least double that figure.
"The global television coverage promoting Cornwall alone would have cost around £12 million.
"Cornwall really got the ball rolling and created a huge surge of interest in the event that rushed in Devon.
"Initially crowds of 20,000 were expected in Plymouth – on the day around 55,000 turned out which was brilliant for the local economy – we estimated the county received an extra boost of between 10 and 12 million pounds.
"The effect the event had on the local economy cannot be underestimated."
In Cornwall there were around 100 events and activities organised by the communities to celebrate the historic journey through the county.
Chris Ridgers, Cornwall Council's portfolio holder for economy and regeneration, said it was undoubtedly a great day for Cornwall.
He said: "The event has been widely acknowledged as a great success.
"The incredible media coverage we received has really put us on the map – sending positive images of Cornwall – both as a destination and as a place with the ability to deliver high quality events – around the world."
The report was pulled together by Cornwall Development Company.
Malcolm Bell, head of VisitCornwall, the county's tourism service, said hosting the start of the Olympic countdown was invaluable to Cornwall's tourism industry.
He said: "The reach has been immense, and thanks to this once-in-a-lifetime event there are now millions of people across the world who have been introduced to the beauty of the county and now may consider visiting.
"The opportunity now lies in building on this success to maximise the legacy for Cornwall and to realise the potential of Cornwall becoming an international market leader for tourism whilst attracting more overseas visitors."
A spokesman for Devon County Council last night said similar figures were not yet available.