Oh come now, that's a bit ridiculous. Interiors are upgraded, accessories are upgraded, often the suspension is upped as well. Outside of that, many of the Lexus models have completely redone power trains (F line). The IS line is on a completely separate platform from whatever the equivalent vanilla toyota would be.
I would have gone with something like Ford and Lincoln, where they really are almost completely rebadged.
As a Toyota fan, who recently looked at both a Ford Escape and a Lincoln Navigator...
You mention "interiors are upgraded, accessories are upgraded" - a 2010 Escape looks and feels cheap. Plastic everywhere, everything creaks and squeaks when you lean on it a little. The Lincoln has (actual) wood paneling, things like retractable running boards and even a nearly ten year old Navigator feels nicer, so I'm not sure how you can say it's not like the Toyota-Lexus difference.
I would have gone with something like Ford and Lincoln, where they really are almost completely rebadged.