Boil the potatoes in a large pot of salted water until tender. When cooked, drain and let cool completely.
To prepare the other ingredients, dice the eggs, slice the pickles and celery into small cubes, and chop the green onions. Place all these ingredients in individual bowls.
In a large bowl, combine the mayonnaise, sugar, vinegar, sour cream, salt and pepper. Mix until all ingredients are fully incorporated.
Add the potatoes, pickles, celery, eggs, and green onions to the dressing. Gently fold everything together until evenly distributed.
Serve this Costco Potato Salad chilled as a summer side dish or alongside your favorite meals.