This was discussed a couple of years ago here.
Here's what I wrote at the time.
Ryanair uses a very simple formula. 1000 passengers per year = 1 job. In the example you give they also imply that each passenger is worth €500 in tourism spend.
It's not difficult
to pick holes in this methodology, but that's how they do it. In the same way, whenever they open a new base they describe it as an "investment" based on the list price of the number of aircraft they plan to base there, even though they haven't paid anything near the list price of the aircraft. But ultimately, it's like the guy in the film Casablanca saying "I'm shocked to find gambling going on in this casino." Ryanair twists statistics to suit its own ends. That's just what it does. Expecting otherwise is naive.