Apple has confirmed the decision to stop using third party companies for cellular modems after Srouji succeeded Rubén Caballero. They’ll continue making A-series chips though.
But, the cost of Apple made modem chips and third party chips differ. Third party chips cost $15 to $20 bucks for each one, and $3 to $4 billion per year per 200 million iPhones. That’s $150-225 approximately a chip for an iPhone.
Overall, this is not the first time Apple has started developing their own chips for cellular modems. Apple went through many rivalries with Qualcomm royalties on chips. This caused to be the reason why Apple used Intel on cellular modem chips on the iPhone.