Overwrite the value in my List but why?

Hi, I create a field of tiles. Every tile is store in a class who also have a list for all neighbours and every neighbour have a float for movement cost. The cost should be different but it looks like the class overwrite the values from the tile befor. I try to make a seperate list for every single node but looks like the value of movement cost is always overwrite but I can't figure out why.

Here the class for the node:

 public class Node {
     
         public Transform tileTrans;
         public List<Node> neighbours;
         public float movementCost;
         public Renderer ren;
     
     //    public Node()
     //    {
     //        neighbours = new List<Node> ();
     //    }
     }

And here the class who seek the neigbours and store it in the list: This class look for every tile and find via raycast the tiles next to it. If the neighbor tile diagonal to it, the neighbor get a movementCost of 1.4f. But when I test the code all neighbors have a value of 1.4f.

 using UnityEngine;
 using System.Collections.Generic;
 
 public class MapManager : MonoBehaviour {
 
     //variables
     List<Node> graph;
     LayerMask mask = 14;
     
 
     void Awake() 
     {
         graph = new List<Node> ();
         GetAllNodesInGraph ();
         GetNeighbours ();
     }
 
     void GetAllNodesInGraph()
     {
         GameObject[] tiles = GameObject.FindGameObjectsWithTag ("Tile");
 
         foreach (GameObject go in tiles) 
         {
             Node n = new Node();
             n.tileTrans = go.transform;
             n.ren = go.GetComponent<Renderer>();
             graph.Add (n);
         }
     }
 
     void GetNeighbours ()
     {
         foreach (Node n in graph) 
         {
             List<Node> neighbours = new List<Node>();
 
             Vector3 originPos = new Vector3(n.tileTrans.position.x, n.tileTrans.position.y + 0.5f, n.tileTrans.position.z);
             RaycastHit hitInfo;
 
             if(Physics.Raycast(originPos + new Vector3(1f, 0f, 0f), -Vector3.up, out hitInfo, mask.value ))
             {
                 foreach(Node hit in graph)
                 {
                     if(hit.tileTrans == hitInfo.transform)
                     {
                         neighbours.Add(hit);
                         hit.movementCost = 1f;
                     }
                 }
             }
 
             if(Physics.Raycast(originPos + new Vector3(-1f, 0f, 0f), -Vector3.up, out hitInfo, mask.value ))
             {
                 foreach(Node hit in graph)
                 {
                     if(hit.tileTrans == hitInfo.transform)
                     {
                         neighbours.Add(hit);
                         hit.movementCost = 1f;
                     }
                 }
             }
 
             if(Physics.Raycast(originPos + new Vector3(0f, 0f, 1f), -Vector3.up, out hitInfo, mask.value ))
             {
                 foreach(Node hit in graph)
                 {
                     if(hit.tileTrans == hitInfo.transform)
                     {
                         neighbours.Add(hit);
                         hit.movementCost = 1f;
                     }
                 }
             }
 
             if(Physics.Raycast(originPos + new Vector3(0f, 0f, -1f), -Vector3.up, out hitInfo, mask.value ))
             {
                 foreach(Node hit in graph)
                 {
                     if(hit.tileTrans == hitInfo.transform)
                     {
                         neighbours.Add(hit);
                         hit.movementCost = 1f;
                     }
                 }
             }
 
             if(Physics.Raycast(originPos + new Vector3(-1f, 0f, 1f), -Vector3.up, out hitInfo, mask.value ))
             {
                 foreach(Node hit in graph)
                 {
                     if(hit.tileTrans == hitInfo.transform)
                     {
                         neighbours.Add(hit);
                         hit.movementCost = 1.4f;
                     }
                 }
             }
 
             if(Physics.Raycast(originPos + new Vector3(1f, 0f, 1f), -Vector3.up, out hitInfo, mask.value ))
             {
                 foreach(Node hit in graph)
                 {
                     if(hit.tileTrans == hitInfo.transform)
                     {
                         neighbours.Add(hit);
                         hit.movementCost = 1.4f;
                     }
                 }
             }
 
             if(Physics.Raycast(originPos + new Vector3(-1f, 0f, -1f), -Vector3.up, out hitInfo, mask.value ))
             {
                 foreach(Node hit in graph)
                 {
                     if(hit.tileTrans == hitInfo.transform)
                     {
                         neighbours.Add(hit);
                         hit.movementCost = 1.4f;
                     }
                 }
             }
 
             if(Physics.Raycast(originPos + new Vector3(1f, 0f, -1f), -Vector3.up, out hitInfo, mask.value ))
             {
                 foreach(Node hit in graph)
                 {
                     if(hit.tileTrans == hitInfo.transform)
                     {
                         neighbours.Add(hit);
                         hit.movementCost = 1.4f;
                     }
                 }
             }
 
             n.neighbours = new List<Node> (neighbours);
         }
     }
 
     
 
     public List<Node> GetGraph()
     {
         return graph;
     }
 }

I guess I do not understand the behavior of List<> and make values store to a List<> seperate and not refer to a value.

Maybe you can help.