They could have achieved higher density, but it would have been more expensive. The density is in service of low costs, so that wouldn't have made much sense.

Difference is the iPhone has insane margins. You want to pay $35 or $100?

Judging by how tight some of those discretes are packed on the board, Apple also has some serious pick and place machines.

It's not the PCB that's expensive. It's the components on it.

That's often not true; PCBs can be a significant cost on the bill of materials for a gadget.

Amortising the tooling / artwork costs into big volumes helps, but even then the PCB is usually one of the more expensive items on the parts list.

Yup, it was interesting reading some of the discussions about the design of the device. PCB cost was a major consideration. They aren't exposing some of the I/O pins on the SoC because it would require a more expensive PCB to do so.

Custom small-time boards get expensive quickly when you shoot for tighter tolerances, which are necessary for truly tight spacing. If Raspberry Pi expects to sell 10 million units, then even a fancy board will cost nothing, but I doubt they are planning on such numbers...

Board design is expensive for small units - but assembly costs for complex boards don't drop very much with large numbers.

Especially if Apple have every super high-end pick and place robot booked for the next n years!

$100? heh the 16gb 4s is $200(+fees, tax, etc.) because its subsidized with a 2 year contract. I think it's something like $650 if you buy it unlocked. compared to a $25 - $35 computer? Apples and oranges ;)

I believe they were implying the R Pi may have cost $100 with a more compact board.