The cost to Wales of the FA Cup returning to Wembley could be as much as £10m, experts say.
But the value of publicity provided to the country by the seven competitions, which ran from 2001-2006 at the Millennium Stadium, is almost immeasurable.
Dr Max Munday, director of the Welsh Economy Research Unit at the University of Cardiff, agrees.
He said: "The FA Cup is unique isn't it? I don't think the rugby matches really replicate it with impact outside of Wales.
"I suppose the only things that could compare would be a Champions League final, which, with the best will in the world, we are unlikely to get.
"There is very little like it elsewhere in the world. It has history and it attracts an international audience.
"The spending of supporters does not really get close to what the real value of something like the FA Cup is.
"It had a massive impact and flagged Cardiff up as a location and as an area of business. The FA Cup is broadcast not just in the UK but internationally.
"Many of the other events that are held at the stadium, like the rugby matches, don't go as far as the FA Cup.
"If you were to try to achieve that coverage through conventional advertising how much would it cost? Measuring that is very difficult."
Fellow university senior research associate Calvin Jones said: "There's a worry that with the loss of business coming to the stadium every year there will be a significant knock-on effect for the businesses in Cardiff.
"It would be in the order of £10m-ish. The stadium itself will be losing out and there will be a big hole there to be filled."
The message is the same from former Russell Goodway, chief executive of Cardiff's Chamber of Commerce.
He said: "It is a significant hit on Cardiff's economy because you're just not getting as many visitors coming to the city and staying for a couple of hours, during which a lot of them spend a significant amount of money."