Without your actual data, it's pretty difficult to be precise, but...
The operator precedence looks right - divide is done before <, so that should be right.
It may be that all ListPrice values are less than 4 times the standard cost: so try this:
SELECT Name AS ProductName, StandardCost AS Cost, ListPrice AS Price,
ListPrice / 2 AS LPBY2, ListPrice / 4 as LPBY4
FROM SalesLT.Product
WHERE
ListPrice / 4 < StandardCost;
And look at what the comparison is doing in each case.
If would probably also be worth reversing the test in each case and seeing what you get back:
...WHERE ListPrice / 2 >= StandardCost
...WHERE ListPrice / 4 >= StandardCost
That should help you work out why - but if not, let me know what results you do get.