I'm more interested from a labor perspective, but practically, you get less money for your work, and no benefit. Especially as a freelancer, paying all your own taxes, insurance, health, and company costs. That means you need an addition 20% revenue, not less.

If you work in demanding field, and have a client that needs—and can afford—your work, giving them them a discount only takes away from your stack. What possible benefit is there? Repeat business? They will repeat if they need it, not b/c it's on sale.

Assume you are literally putting money in their pocket (ROI) and get paid what you're worth.