Article got accepted into PRL -- do I pay the costs?
What are your options? You can pay or delete the email.

If you pay, your group will have $765 less. That's the only difference in outcomes. These charges are completely voluntary and have no effect on anything if you choose not to pay. In my experience, you'll never hear about this again. You will not have to justify your decision.

What do most people do? From my observations, the majority of groups simply don't pay voluntary charges, regardless of available funds.

What should you do? This is a matter of opinion. You (or the PI with the money) should decide whether APS deserves a $765 donation for the purposes they state, or whether it can be put to better use at your institution.