I was researching some plain vanilla option American/Option data and I found some European option which are more expensive than there American counterpart (all other factors are equal, except for the volatility). As you all know (and I also have learned), the price of an European option is always lower or equal to its European counterpart. I first thought that it was an error but I found many more cases and it looks that it is caused by a lower volatility for an American option than the European counterpart. See also the example below. What could be a reason for this? It does not make sense to me that these two are different.