Last week, the IRB revealed that the 2015 World Cup hosts would have to pay the sport's governing body £100 million, while the 2019 hosts would be charged £120 million.
O'Neill (pictured right) said that only countries such as Japan, England, France and Australia would be able to afford to host the tournament and he warned that governments would be loathe to pay that amount of money.
"Australia has led the way in supporting major events in cash and in kind," O'Neill said.
"But those £100 million, £120 million for 2015, 2019 are at a level that we haven't seen before.
"It's almost saying it doesn't matter if the host doesn't make a profit.
"You could end up with a situation where the Olympics were in 1984, when they couldn't get anyone to host the Olympics and Los Angeles stepped up and did so on their own terms."
New Zealand are holding the 2011 World Cup and the IRB is scheduled to announce the hosts of the following two tournaments next July.
The outspoken O'Neill also took a swipe at the major European unions over their reluctance to introduce rule amendments made under the Experimental Law Variations.
He said the first two Tri-Nations tests between New Zealand and South Africa had highlighted the importance of accepting the ELVs.
"The first two test matches played under the ELVs have been absolutely fantastic games," he said.
"And that's what ultimately will catch up with the Northern Hemisphere.
"One day, the fans will say this is boring, you know, penalty shootouts are not what we've come to see."