// int64 list
var valuePrices = new List<Int64>();

// string
var price = "175000+200000";

// convert string to string list by Split
var stringPrices = price.Split('+').ToList();

// stringPrices
// [0] : "175000"
// [1] : "200000"

// convert to int64 list by ConvertAll
valuePrices = stringPrices.ConvertAll(Convert.ToInt64);

// valuePrices
// [0] : 175000
// [1] : 200000