Earlier quoted context omitted.
Yes Walmart is the textbook example of a monopsonist being able to extract steady profits while creating a race-to-the-bottom for prices among their suppliers. Great for end customers, but harmful nonetheless.
I don't agree Walmart would make for a textbook example. I'd argue they were/are not even a monopsonist with regard to their suppliers. They might be a strong regional force but they have failed (or chosen) to move out of their regional power position. That's not a bad thing and in fact is a strength. I'm pretty sure they were cited as an example of good strategy for exactly that in "Competition Demistified" but don'…
You've never sold to walmart, I have. If they put your physical product on the shelf you'll sell a lot of units. No one else has the shelves walmart does. If you are not on the walmart shelf there is NO way to get the same number of units sold.