It’s not like a customization in terms of adding your name as an example.
Are you kidding me?
Engraving your name, any text, or an emoji is the same customization service. Emojis are just added to that service.
And again - you were claiming, that customers had to spend extra money for this (your words, not mine). And this is complete false information.
Using this service will not result in any
additional costs - so it's basically for free.
AirPods without the engraving will cost absolutely the same.
For Apple, the engraving not for free. The engraving doesn't fall from the sky, but it also doesn't cost a fortune. It's a fully automated process of laser engraving. The laser that prints the "Designed by Apple" claim on the AirPods' case is just printing the additional custom text or the emoji. It will only take a tenth of a second and will cost almost nothing.
They don't have to charge the customer for this, because a customized product cannot be returned. So they reduce their total (estimated) cost by investing less than a little.
But yes, your'e kind of right...
Any product price of any company includes lots of secondary and tertiary costs to keep the company running, develop new products, advertise them, support the current ones, paying your employees and partners, making profit, and so on...
With every Apple product you buy (physical or virtual), you're also paying for many free events and sessions Apple holds - even if you participate or not.
Thats how every business works.