using System;

using System.Linq;

using System.Collections.Generic;

using System.Globalization;

​

public class Program

{

    public static void Main()

    {

        var list = new List<string>{"3,200,000.00", "2916410", "28,710,000.00", "0.80000000000291", "-1000000"};

        var sum = list.Sum(x => decimal.Parse(x, NumberStyles.Any, CultureInfo.InvariantCulture));

        Console.WriteLine(sum);

    }

}