Compact density is expensive, cellular is expensive, and the iPhone has to pass all-day battery and pocket bending tests. (Edit: also being dropped on gravel)
In addition to the iPad having cheaper parts than the iPhone, the iPad reuses many of the same components for several years. The current iPad uses the same display as the previous generation iPad that was released in 2022 - three years and counting. But every single iPhone generation has changes to most of its components, and every single year has a new iPhone.
I'm sure that they have a fatter margin on the the iPhone, but the iPhone does cost quite a bit more to manufacture. Cellular itself is probably $50 or so. The iPad has more material, so you may perceive you're getting more "device per the money" but the cost of those materials is dwarfed by the cost of manufacturing the additional components.
This is incidentally why consumers don't buy small phones even though they say they want them. They feel cheaper even though they cost about the same to manufacture.
> This is incidentally why consumers don't buy small phones even though they say they want them. They feel cheaper even though they cost about the same to manufacture.
Actually from what I understood, making a small display with modern specs like Apple did on the iPhone mini was MORE expensive because all of modern high-end smartphone display manufacturing is designed for larger, 6+ inch screens.