Yup, it's a bad example for the reason you mention.
Putting that aside though, once you're out of positional good territory some providers of goods and services are indeed willing to accept different prices from different customers depending on their capacity to pay.
If I can make 10% profit out of you by charging a lower price whilst still being able to make %200 profit from the next client through the door because they can pay more, then it is rational for me to do so. The trick is that it is difficult to convince rich client A to pay twice as much as poor client B if A knows that B is getting the same good for half the price, but if you can pull that trick off, then it is totally rational to modify the selling price based on the customer's capacity to pay.
Putting that aside though, once you're out of positional good territory some providers of goods and services are indeed willing to accept different prices from different customers depending on their capacity to pay.
https://en.wikipedia.org/wiki/Market_segmentation
If I can make 10% profit out of you by charging a lower price whilst still being able to make %200 profit from the next client through the door because they can pay more, then it is rational for me to do so. The trick is that it is difficult to convince rich client A to pay twice as much as poor client B if A knows that B is getting the same good for half the price, but if you can pull that trick off, then it is totally rational to modify the selling price based on the customer's capacity to pay.