Applying a currency symbol based on a tested string value
I'd create an NSDictionary holding those prefixes and wrap that whole thing into its own method, like so: 

-(NSString *) prefixForCurrency:(NSString *)currency{
    NSDictionary *currencyPrefixes = @{@"EUR": @"€", @"USD" : @"$", @"GBP" : @"£", @"NOK" : @"kr." };
    NSString *returnString = [currencyPrefixes objectForKey:currency];  

    return returnString;
}


Then, instead of your current mass of if-statements you'd have something like the following:

NSString *currency = [item objectForKey:@"currency"];
NSString *currencyPrefix = [self prefixForCurrency: currency];

NSString *price = [item objectForKey:@"price"];
NSString *priceString = [NSString stringWithFormat:@"%@ %@", currencyPrefix, price];


In case you were wondering: the main reason I wrap the prefixDictionary in its own method is in case you'd for instance prefer to fetch this list from a file later on. Then you can just alter the innards of that one method...