Correct me if I'm wrong, but your comment here gives me the impression that you are asking an awfully general question, but actually want the answer to a very concrete question: "Should I study X at a top uni abroad, any uni at home, or not at all, given that I'm good enough to choose myself but will have to make debts to study". This would be a much easier question for us to answer, especially if you tell us what X is, whether you'd want to continue with a postgrad, and maybe what you goals are for the time after your studies. It's perfectly ok not to know all of these yet, but some info would help.

Yeah, Cambridge is pretty expensive. (I think the best US universities are a lot worse, but haven't actually looked at the numbers. Some or all of these places may have some kind of assistance available if you're very poor or very good or both.) The recent reduction in the value of the pound (because of all the "Brexit" hoohah) has made UK universities a bit cheaper for foreign students.

I'd hesitate to call anything universal, but I'd consider at least the following things. You've probably thought of them all already :-). Some of them are awfully hard to assess. You may be able to get useful answers to some of them from the universities themselves, though of course it may be in their interests to mislead you or to refuse to answer some kinds of question.

• How well do the courses available match what I am actually interested in learning?
• What possible career paths might I follow, and will going [wherever] and studying [whatever] help with them? (Be realistic!)
• Will I enjoy my time there? (This depends on things like climate, culture, difficulty of course, interestingness of course, other people there, ...)
• Will I meet plenty of people who will be friends, mentors, useful future contacts, etc.? (How much this matters, and how much use you can make of the meeting-people opportunities, depends on your goals, personality, etc.)
• Will my having gone there impress people? Will I care?
• Will the academic work be too easy or too difficult for me?
• Is it assessed in ways I can do well at? (I'm not sure how much this varies. But e.g. there may be variation in whether it's only your final year's examinations that count; in whether there's coursework as well as examinations; in whether some examinations are "open book".)
• How much will it cost? (Take into account any scholarships, bursaries, loans, etc., available to you.)
• If while there I find that I want to be doing something else, how flexible will they be? (At some universities, perhaps all, it's pretty easy to change subjects, at least if you're moving from a "harder" to an "easier" subject.)
• Will they actually have me? If it's uncertain, am I giving up better opportunities by trying?
• If the university is abroad, will I face prejudice from the locals? Or feel prejudice myself against the locals? How comfortable am I in the local language? How comfortable am I with the local culture? Will the food etc. be OK for me?
• How do they teach? What's the actual quality of teaching like? Will I be being taught by world expert researchers or struggling graduate students? (Note: the former are not necessarily better teachers.)

Israel has great tech universities.

Oxbridge and other UK universities are chronically underfunded because of regulations about how much they can charge domestic students, so they try to make up for it by charging foreign students big money. My guess is that elite US universities are much better value-for-money for foreign students.

I just looked at the Cambridge prices for overseas students and it made me feel poor. Might as well seen a 500,000 ILS debt in my bank account.

You might be able to get financial aid or scholarships, so I wouldn't rule out an expensive university right away. If you apply and get accepted, which admittedly itself costs some money, then you could have some talks with the financial aid people. And their first answer may not be the final answer, or there may be alternative sources of funding, so you may have to repeat yourself and keep talking to them for a while before you together figure out something that could work. Some universities claim to have the attitude that they don't want anyone to not be able to attend because of financial reasons, but in practice it is hit and miss to get them to live up to it, and easy to get into debt. It may depend on the individual person you are talking to. If one person isn't helping much, a different person in the same department may help more. Sometimes people unfamiliar with the system get discouraged by the first thing someone in financial aid says to them and walk away, instead of advocating for themselves more, or exploring the problem from a slightly different angle.

You may also want to look into universities that have a co-operative education program that involves paid work in between sessions of study. This won't completely pay for the costs of education, but it can help a lot.