Why does appending a value to a list take more storage than a list literal?

I have provided 4 different ways to fill these lists with the same value:

var = 'a'
print('var id: ', id(var))                # var id:  1561191205488

lst1 = [var]
lst2 = ['a']
lst3 = []
lst3.append(var)
lst4 = []
lst4.append('a')

print(lst1.__sizeof__(), id(lst1[0]))      # 48 1561191205488
print(lst2.__sizeof__(), id(lst2[0]))      # 48 1561191205488
print(lst3.__sizeof__(), id(lst3[0]))      # 72 1561191205488
print(lst4.__sizeof__(), id(lst4[0]))      # 72 1561191205488

print(lst1 == lst4 == lst3 == lst4)        # True

I know that in Python everything is passed by reference and in those lists, the actual value that the list stores is a reference to the object 'a', and they are all the same (as I printed the ID's).

I expected that at least 'lst2' and 'lst4' and also 'lst1' and 'lst3' have the same memory usage, but they don't! It seems like the append method does something more than storing the reference...

Could anyone tell me what's going on here?