I attended an Ivy in the eighth decade of the twentieth century. I well remember the professor in a large lecture course going to the chalkboard, drawing an approximation of a bell curve, and dicing it up to show us that about 10% of the class would get an A, while a similar number would fail; about 20% would get a D, and another 20% would score a B; and 40% would end up with a C. The average GPA of my graduating class was 2.xx, and a C was a perfectly honorable, if not particularly desirable, grade.
That was then. Since then, all--as near as I know--of the Ivies have experienced considerable grade inflation. I'm told (yes, correct me if I'm wrong) that Harvard recently toughened its standards, and now only about 70% graduate with honors, compared to 90% a few years before. (Other Ivies are similar, if not quite that generous.) Like most other colleges at present, the Ivies seem to have made a B or even B+ the default, "average" grade.
A lot of kids at Ivies get a lot of As. But so do a lot of students at a lot of other colleges. So is Ivy coursework more difficult? Well, from what I've seen (a very unscientific sampling), the Ivy students do a little better work for their grades. They're less likely to get an A for a paper riddled with spelling, punctuation, and word-usage errors--compared to some other colleges (including quite a few well-regarded ones), where simply completing an assignment and turning it in on time makes it a presumptive candidate for an A.
[Having said all that: my mother-in-law used to be an Ivy League professor. Once she very proudly shared with me a major paper written by one of her students. I'll grant this: the student had obviously done a *lot* of work, researching (including field work) and writing the paper. But the paper had so many errors in English within it, I literally couldn't finish reading it. My MIL gave it an A+.
[What gives this a different angle is that the student was a person of color. I frankly cannot imagine an identical paper, written by a white kid from Scarsdale, getting the same grade or anything close to it.
[So, in addition to grade inflation, there is definitely an element of social engineering within the grading--at least of some courses. And this too affects how truly difficult it is to get a good grade.]
Long story short: Ivy coursework and exams may be marginally more difficult than those at most state schools (where many courses are truly a joke), but the students mostly end up with As anyway.