surely not,
I see what you are saying but the huge savings being made by the original poster leads me to believe that this is probably, two non flexible cheap tickets versus a fully flexible ticket.
The problem with all of these scenarios is you get what you pay for. The more expensive ticket will be totally flexible and the cheaper option would not be at all flexible.
We will no doubt get yet another post, in the future, of people moaning that they can't change the date of their cheap ticket and how unreasonable this is. but that's life.
I find you usually get what you pay for, cheap is not always good.
Everyday I see passengers who have gone for cheaper options like buying connecting flights separately and not leaving enough time between the sectors but often it all comes undone when you get delays for weather or as at the moment French Air Traffic control.
Those that paid for the flight as one journey get hotel accommodation and automatically re-booked if they miss the connection but those that did DIY get no hotel, no refund and have to spend ages trying to book another flight themselves. As a crew member I see it all the time and it really is a false economy.
So as I say, in life you usually get what you pay for, the choice is yours.