So, while your experience may vary, here was today's story. I went to the website to purchase a same day Colonia return (AR site, in AR). The site wouldn't even permit a same day return as transport only, although did offer same day tour packages. No, I'll pass, and walk to the terminal, close to home. After waiting in a short line (that took nearly a half hour), the clerk said that for the next few days, there were no promotional tariffs available, only the full fare (approx. US$100 each, had I paid cash). I asked her about packages, and she said there were none, only the full fare tickets.

Ok, whatever, we left. Maybe the tour packages had sold out. And there's always a Buquebus option to check.

Returned home, went online, packages available two days out (walking tour, walking tour with lunch, bicycle tours), and with the CC rate not being bad, bought the walking tour (no lunch) for about $61/pp when I checked my CC. Saved nearly $80, and maybe we'll learn some history. And I suppose we can always ditch the tour if it is too annoying. And now, we know exactly where to go, because we've been to the terminal. Exito!