Earlier quoted context omitted.
More expensive is OK, significantly thicker and heavier is a deal breaker.
I guess, but would you consider the existing 13" MBP to be "significantly" thicker and heavier? There's already very little differentiation between the models.
On a purely numbers basis, the difference doesn't seem significant (hence how I talked myself into the purchase), but there's a massive "human scale" threshold that's crossed in that difference. IMO, an 11" MBA feels more "like an iPad" in those respects vs. a 13" MBP very much feeling "like a computer".