In Germany, and this might apply to other states of the EU too, you'll pay a fixed percentage of your loan for healthcare services. For Germany it's around 14-15% of your monthly income before taxes. So, if you earn well, you'll also have to pay a bigger sum for healthcare services.
Health insurance is capped in Germany. We have the very German word "Beitragsbemessungsgrenze" for that.
Basically, the insurance cost is a percentage of income (14.6%) up to 4,537.50 €/month (gross income). If you earn more, your absolute health insurance costs will stay the same at 662.48€.
Keep in mind that in Germany, half of your health insurance is covered by your employer (by law).
Edit: The above is for the "public" insurance system, as noted in the comments. If you are above the Beitragsbemessungsgrenze, you can opt for private insurance which will very likely be significantly cheaper while you are young. But it carries the risk of steep price hikes which you might not be able to handle later in life (think retirement). And the path back into the public system is not straight forward and might include having to file for personal bankruptcy or similar drastic measures.
If one was naïve enough to choose private insurance (because they earned more than the threshold where it's possible to insure yourself at a private provider), it can get up to 1000€/mo pretty quick. Not in your twenties but beware the forties.
When less than 45 years old and married with a spouse covered by public insurance, it may be worth taking a year off work (e.g. a sabbatical; must earn less than EUR435/month) to undo that damage.
(Details:
You can go back once you're covered by public insurance for 12 months, no matter through which status, so family insurance helps get these months. For family insurance your income needs to be below EU435/month + some exceptions.
The outcome changes a bit when you're older than 45 because you need ~20 years (in raw terms: more than 90% of the second half of your working life) in total in the public insurance scheme to be able to apply for the "public health insurance for pensioners" system when you retire. That complicates matters.
Even more details for people not used to the German health insurance system:
By default people are in the public health insurance system. Exceptions are self-employed folks, public officials and people with income beyond the cap mentioned upthread: they can choose whether to use the public system or some private health insurance.
The reason why you can't just move from private insurance to public insurance is that otherwise the private insurers would try to get ahold of all the healthy youngsters and their (usually significant) money while offloading them to the public system as soon as they start to cost more than they bring. That would break the economics of the public insurance system.)
No, the 15% is just Krankenversicherung (health insurance). There's also Pflegeversicherung (nursing care insurance), Arbeitslosenversicherung (unemployment insurance) and Rentenversicherung (national pension fund).
When I take an average salary (3000 euro monthly gross salary) and put it into a tax calculator, the net salary comes back as about 1950 euro, so the different between gross and net salaries is about 35% in that tax bracket.
It's 14-15%, but half of that is covered by the employer (outside your gross pay).
So if you earn EUR 1000 (just to have a nice round number), it's EUR 150 for health insurance, of which EUR 75 come from your gross pay, and another EUR 75 are itemized as coming from the employer.
That makes the 14-15% look scarier than they are (for the employee).
If you earn more than 50k Euro per year you can opt in for private health insurance instead. This greatly reduces the cost of insurance if you have big income. You can get good private insurance for 250-400Euro/month depending on your age.
... which will balloon to 600, 800 Euro/month, as you get older. And if don't maintain the same level of income as you retire, you might have another thing coming - the public insurance will not welcome you back.
I find this perfectly valid and think we should get rid of private health insurance at all. It's undermining our system, pretty much like pension for state workers and alike. We really need to unify this system, imho.
I have never heard of such outrageously priced healthcare plans (private providers excluded, of course).