Managed to get rid of some lines of code..

private decimal ConvertStringToDecimal(string decimalString, decimal defaultReturnValue)
{
    decimal value = decimal.TryParse(decimalString, out value) ? value : defaultReturnValue;
    return value;
}

You can write the equivalent shorter, using the ternary operator ?: and decimal.tryParse, like this:

private decimal ConvertStringToDecimal(string decimalString, decimal defaultReturnValue)
{
    decimal value = decimal.TryParse(decimalString, out value) ? value : defaultReturnValue;
    return value;
}