the retail value of the phone is $640. Of course, the retail price is one thing, but the manufacturing costs are quite another.
iSuppli mixed together the known components like the Exynos Octa SoC with some educated guesses on other parts and has estimated that the HSPA variant of the Galaxy S 4, with the Exynos SoC has build materials costing $236, and an $8.50 manufacturing cost, putting the phone at around $244.50 to build. The LTE variant which has the Snapdragon 600 comes out slightly cheaper with build materials costing $231, and the same manufacturing cost, putting the total at around $241.50.
These are estimates of course, but should be pretty close to reality. And, that means that Samsung has put about a $400 markup on the phone.