Thunderbolt has been royalty-free since 2019, when it was licensed to the USB-IF to be used as the basis for USB4. https://arstechnica.com/gadgets/2019/03/thun

Thunderbolt has been royalty-free since 2019, when it was licensed to the USB-IF to be used as the basis for USB4. https://arstechnica.com/gadgets/2019/03/thunderbolt-3-becomes-usb4-as-intels-interconnect-goes-royalty-free/ https://arstechnica.com/gadgets/2019/03/thunderbolt-3-become... (I also suspect that Apple's cut wasn't huge to start with; Thunderbolt was developed with Intel, and Intel likely got the lion's share of royalties given that they were the ones actually selling the Thunderbolt controllers and seem to have been the driving force behind Thunderbolt 3.)