if you get into metal detecting thinking you are going to get rich find a different hobby, but on the other hand if you are looking for a hobby that gets you outside just to have a great time then by all means get a metal detector you never know what you will dig up
If you live in FL and CA near the beaches, yes from a monetary stand point you can find expensive rings once you learn how to beach hunting.
Not sure about Europe.
For me it just is the fun of the hunt. Each signal can be junk or treasure. So you really don't know, and that is part of the fun as long as you do find some treasure. Yes 2-3 hunts not finding any good stuff can be frustrating, but if you realize it is a hobby and not a business you take those days not finding much in stride.
I UK and Europe you guys have a shot at much older and more valuable coins. In the US our people have been dropping coins for a couple hundred years not thousands of years. So you guys in Europe have a larger upside than we do in the states.
Short answer, NO. If you save all the coins and jewlery you find over twenty years you might be able to pay for one knee replacement if you are lucky or have access to a beach in front of a five star hotel. And that's assuming nothing else goes wrong like shoulder, back, hips, wrists, elbows, just about every joint on your body gets stressed. I hurt my leg muscle and it took about two years of pain to recover, just from standing back up after digging.
But gamblers are gamblers. I watched the poker on TV. One pro his family had to take away his credit card. Another lost 22 million is four days and never got it back. At least with MD you don't have to gamble a bunch of money, just your health. Don't buy the crap about getting healthy from detecting. I worked four or five hours every day for a few months and never lost one pound of weight. But it's something to do and you never know what will come up next target.