He is assuming you set individual prices per customer or basically that each customer has his or her own demand elasticity.
What you are thinking of is a market demand, which is a useful approximation when the market is large and anonymous.
Instead, he gets at the idea that each customer has an individual reservation price, upon which he will still buy your service or good.
If you manage to ask exactly this price, you can extract the maximum profit from each customer.
Edit: I could do a write-up of the details. I don't have a blog or something like that tho.
What you are thinking of is a market demand, which is a useful approximation when the market is large and anonymous. Instead, he gets at the idea that each customer has an individual reservation price, upon which he will still buy your service or good. If you manage to ask exactly this price, you can extract the maximum profit from each customer.
Edit: I could do a write-up of the details. I don't have a blog or something like that tho.