ExclusivePrice, quantidade são ambos NSDecimalNumbers.

NSDecimalNumber *price = [exclusivePrice decimalNumberByMultiplyingBy:quantity];
NSLog(@"%@ * %@ = %@", exclusivePrice, quantity, price);

O resultado que eu recebo:

2010-04-05 00:22:29.111 TestApp[13269:207] 65 * 2 = -0.0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000007169919476068871316457914368

O que eu esperava:

2010-04-05 00:22:29.111 TestApp[13269:207] 65 * 2 = 130

Alguém pode explicar isso, por favor?

Editar:

Reprodução completa:

NSNumberFormatter *formatter = [[NSNumberFormatter alloc] init];
[formatter setNumberStyle:NSNumberFormatterDecimalStyle];
NSDecimalNumber *n2 = (NSDecimalNumber *)[formatter numberFromString:@"2"];
NSDecimalNumber *n1 = (NSDecimalNumber *)[NSDecimalNumber numberWithInt:65];
NSDecimalNumber *n3 = [n1 decimalNumberByMultiplyingBy:n2];
NSLog(@"%@ * %@ = %@", n1, n2, n3);