Yes.
Phil Ruthven is technically correct, but in practice for the majority of people he's wrong.
But if the average Joe does not save the difference, they'll be massively worse off, and in 20 years time they will wish they'd bought their PPOR (even if it doesn't appreciate much) for the forced saving it provides.
Peter
Our experience bears this out. Bought our 1st IP in the 80's borrowing at 17% interest that increased to about 21%. The only good thing that came out of that whole period was the enforced saving which (eventually) set us up for the rest of our IP purchases. It was scary and stressful and we lived hand to mouth for awhile until I came to terms with the fact that it wasn't the roof over our heads and that we could sell and cut our losses, if need be. We didn't sell and all came good.
Cheers