Still the vast majority do not use them.

That's their entire point.

Extreme price discrimination against people who don't know better/don't bother/etc.

McD has the most generous coupons in their apps among fast food chain and there is basically no limit.

It depends on the market. I worked at the East Palo Alto McD while I was getting back on my feet a few years back and we had hours where 60-70% of the orders used the app in some way. I’d say probably 35-40% of our customers used the app; of regulars, more than 50%.

I was JUST looking at that location because it's about the closest to me. I'm between EPA, University Ave, Menlo Park, and Stanford locations: 6.59, 6.69, 6.09. Meanwhile, Foster City is only $4.99!

Interesting.

Note that the price was $6.69 at that McDonald's and the one at Stanford Shopping Center. But it was $6.09 at the locations on El Camino Real in Redwood City, Menlo Park, Palo Alto and Mountain View.