The SAT Reasoning Test costs $50, whereas the SAT Subject Tests cost $23 as a base price, with additional expenses added depending on which type of test you take (either $12 extra or $23 extra). Fee waivers are available for those who qualify – just see your school’s guidance counselor for a fee waiver application.
You definitely want to register on time for the SAT, though. You'll be paying more for the SAT if you register late!
More SAT FAQ's