you can grow to enjoy anything if you really want to. no job is perfect, and the grass is always greener on the other side. having a law or commerce degree is no guarentee of anything, competition is fierce, and imo the jobs are pretty shit, knowing quite well people who work/worked in those industries.
as i get older things like money matter less and less. dont get me wrong, money is important and its nice to be comfortable, i wont be taking a vow of poverty anytime soon. but ive come to realise you only need so much money, after which it can become a hindrance. i know a few people who earn too much money. they're too young and they have too much cash and they squander it on stupid shit including drugs, which is going to end up causing them serious issues. its different when you have kids and a mortgage, but for most of us that isnt going to happen anytime soon. my point is, how much money do you actually need? i find that once i reach a level i deem comfortable, i dont really need any more. who really needs $250k a year? is it going to make much more of a difference than $100k a year? maybe your couch will be more expensive, your tv a bit bigger, and your car a bit nicer, is it worth it if you have to go to a job you hate every day?
there is no right or wrong here. some people are genuninely fascinated by financial markets or the legal system, and will go to work in those fields and do well, and probably make a lot of cash. they'll pay a price though in their own way, but even then, theyd probably be working in that field even if it wasnt as well paid. there are a lot of people who are drawn solely by the money, enter midlife crisis where accountants start buying harley davidsons and dying their hair blue. take a look at your teachers. if they're over say 30, chances are they were top of their school & at university, and gave up potentially lucrative careers to teach.
another thing is, you dont get rich working for someone else. if you have a genuine passion for a field and the right spirit you can make a lot of money. there is plenty of money in maths and science, if you're so inclined. if you not, theres many careers that are rewarding and fufilling, sure they're not as well paid, but gee, they're really interesting and cool. you also write off the chance of making money. senior lectures in science/maths will make in excess of $100k, get to do cutting edge research with world class peers. also, even though salaries may be low, companies will fund academics to do research for them ala research grants, and these can be quite substantial, so at least you get to play with some cool toys, that most people in industry only dream of. if you dont become an ardent academic and keep some sense of business perspective theres a lot of money to be made.
fulltime work is enjoyable for approximately three months, then it becomes a chore, then you grow to hate it. if you really hate it you can go back to uni and do something else which is fairly common. i can safely say ill never use around 90% of what ive been taught in my comp sci degree in the workplace, but im thinking of doing a phd, just cause it will stimulate the intellectual interest i have in computing, which is moreorless irrelevant in a typical IT job. so, i work to pay the bills, and do something pie in the sky simply cause i enjoy it.
if i were you, id use google to find a few people who have phds in your chosen field and mail them, and see if they regret it. also find some people in law/whatever and mail them. it seems a bit weird but ive done it myself, and people can be surprisingly open to random people on the internet.
in my experience its hard to get good advice. your parents want you to look after them once they retire (they might not say it but its true), your teachers are too in love with education to be practical, and your career advisor at school probably isnt much use (mine told me to be a security guard). id get your first degree in a science and work for a few years. if you dont like it go do a masters in something else. after that you'll probably have a fairly unique combination of qualifications too, which can lead to interesting roles. dont spend 10 years at uni covering all possibilities & dont get a phd with no commercial experience unless you want to be a career academic.