Walmart's annual profit is ~$130B so what I'm seeing is that yes in fact it's perfectly feasible for 1.6M Walmart employees to get a $40K/yr raise.
Companies like Wal-Mart generally have low profit margins, because there's not much of a barrier of entry and no valuable brand or intellectual property.
Walmart's profit margin is generally 2-3% and is generally $10 - $20B per year. [1]
And if Walmart were making $100B, the comp for their CEO be far from a major expense to the corp.
EDIT: To be clear, Walmart's revenue in 2020 was 559 Billion with a B[0].
We can see on that table[1] that if we take the values listed in the "Total Revenue" row (559 Million with an M, 523 Million with an M, etc) and multiply them by 1,000 according to the directions ("All numbers in thousands") on the chart that we get a result which aligns with reality.
To be even more clear, we can take the values listed in the "Gross Profit" row, multiply by 1,000 as instructed by the directions, and see that yes Walmart's annual *gross profit* is ~130B
138,836,000 * 1,000 = 138,836,000,000
[0]https://www.forbes.com/sites/shelleykohan/2021/02/18/walmart...
Edit: yes, Walmart's revenue is 500+ billion. What does that have to do with anything discussed here? temp667's comment is correct.
Edit 2: first you didn't understand what "revenue" is, now you don't understand what "gross profit" is.