>>105581184
Yeah that's not looking like one you have to turn.
Some watches you have to pry open, so if you look at it from the side, see if there's some sort of place to do so (you usually need a very thin tool or screwdriver). Picrel shows the process.

I'm not in the super low pricing areas personally, so maybe some other anon can give you better advice (I'd have to make guesses basically).
For the upper limit, a _good_ automatic mechanical watch is around 40-45€. That's about the price of a timex weekender (proper brand, but a quartz watch), except it's an automatic with a reliable movement.
My gut feeling is around the 10-15€ mark for a digital or analog quartz with no additional features (for the analog one, the digital can have those features with little additional cost, I'm thinking aspects like a chronograph, maybe even a date dial).
But I don't doubt if you don't need a chronograph you can get a good one for less.
Watches are very subjective in the end after all, so you should make sure you actually like how it looks.

Hell a genuine casio f91w is something like 15€ and will probably last you a decade or more - if you don't mind how it looks.