Work canteens are usually subsidized. There's no way you get this much food for that price and not have it be total garbage. Even with the scale on which a large caterer operates.
Consider that all these lunches are subsidised by the company, which if you think about it could have either completely subsidize or pay workers more and make lunches full price. This lunch format easily costs 8€ or more full price.
Side note: I actually do like for companies to subsidize lunch since it's usually money that is exempt of taxes up to a point (depending on the region) so the workers save money by doing so.
I do like it as well when companies subsidize lunch, but one downside is that in practice, people with certain allergies can't enjoy those schemes some/most/all of the time. While seeing their coworkers enjoying cheap food.
It's win-win for the business. They use the money that could go to salaries to encourage employees to work more hours by staying in the office for lunch.
Maybe its because its of a work canteen, but would like a source there lol, i have never seen anything like that for such price, not even in schools you get it for that price so unless this is a very specific situation where that price for lunches is part of the contract i doubt its real (im from spain btw)