In a travel book, they said that they serve a simple coffee for only 0,09$ since 1924.. is that true ?

That may be price when they opened, but not true today. However you can get coffee for less than $1

I think that is just part of the nostalgia, but I promise you nothing is overpriced here.

That must be an old review. Coffee is still available inexpensively, but not as low as the book states. I checked a review of mine from a year ago and I posted a price of 46 cents then.

I believe it's less than $1 but it's good pricing for the quality.

Not 9 cents. I believe it is 45 cents. Everything is reasonably priced and delicious.