No one is saying students from grade deflated schools like Princeton, MIT, UChicago will get adcom's boosting their GPA by ~0.6-0.8 points. That's unrealistic. Rather, in my experience, grade deflation normally hinders A- students (3.7) who consequently get a B+ (3.3). This 0.4 difference hits your GPA when you're only taking four classes (reducing your overall by about 0.1). So I don't imagine we would get much of a bump beyond 0.1-0.2 GPA points. If you're on the lower end of the affected range, you'll probably get ~0.2 GPA points higher. If you're on the higher end of the affected range, as in close to A-, you'll probably only get ~0.1 GPA points higher. These are just my approximations based on percentiles.
A ~3.66 GPA at Princeton is a ~3.8 GPA at Harvard (which has ridiculous grading, with the median grade an A- and the mode an A). So that's bumped literally in between a 0.1 to 0.2. And this is only relative to Harvard, keep that in mind.