I think a grocers could absolutely do the online ordering and pickup/delivery space where prices could be tailored to individual consumers and there was market dominance.
Sorry, I don't have the data to give a figure. I'd have to build the model, and have a complete transaction record dataset.
Their typical net profit margin is in the 1-2% range.
I'd wager that in 10 years (2034) we won't see that go up substantially -- that it will not regularly be reported to be greater than 2%.
If Kroger is able to do what you're alleging is possible, what do you bet their profit margin will be at that time?