On the Mathematica Store, there are plenty of different licences:
What is the difference for between the three Mathematica | Desktop licences? In the comparison by Wolfram themselves, I can find the following differences:
However, I am already able to use Mathematica | Online in a web browser and on my mobile devices without any subscription. So why does one subscription cost $\frac74$ as much as the other?
Also, what is the difference between annual and one-time plans? Are updates "free" when you pay yearly? Or do you only get the newest version only every year? More specifically: What is the difference between paying 80€ yearly or paying 160€ one-time? And what is the difference between paying 80€ yearly or paying 120€ or 140€ yearly?