Subjects at high school level for pre- med

Yes you should be studying math at highschool not only if you plan on doing premed but for nearly all potential majors. For selective schools, most of them like to see at least 3 years of math regardless of your major. Math is especially important for premed though so I'd recommend taking for years. Subjects like calculus and statistics are also important for pre med so it's a good idea to take those. The cost for studying premed doesn't differ from studying anything else, so it's just the cost of college.