Yes. Booking the flights, the transfers and the park entry separately comes out around 30% cheaper than the packaged day. We would rather say that plainly than pretend otherwise.
Now the other half of it.
What you are taking on
A one-day trip to Iguazú is a chain of bookings that all have to hold on the same morning: a 4:30 am pickup in Buenos Aires, a specific early flight, a transfer waiting at Puerto Iguazú, park admission, and a return flight late enough to make the trip worth taking. Argentine domestic schedules change more than you would like, and a moved departure ripples through everything behind it.
Break one link and you do not get a worse day, you get no day. There is no second flight and no second attempt. It helps a great deal to have some Spanish and to be comfortable re-planning on the ground.
The middle option
If you want the saving without the whole coordination problem, there is a land-only package at US$ 370 per person: you book your own flights, and the transfers, guide and park admission at the Iguazú end are handled for you. That is the half of the day that is hardest to arrange from abroad, and it leaves the half you can do from a laptop to you.
Whichever way you go, the flight pair is the decision that matters. Almost everything else can be fixed on the day. That one cannot.
