I estimate it would cost around $300-500 to get assembled depending on volume. That's just the assembly price. This is based on some online quotes with 15k pads (I checked 25-100 boards).

Then you have actual BOM cost which is maybe another $150-200. A 2N7002 is about $0.02 even at 100k volume. Resistors and small passives are often free, and the remaining bits are cheap.

The board is probably $100 each in small volume. Big four layer beast, not cheap.

I used www.7pcb.co.uk and Mouser/Farnell for prices.

So we're looking at a cost of up to $700-800 plus taxes and shipping. That's without any kind of profit for the designer, distributor cuts and so on. At $1k they're breaking even, $2-3k would be standard markup to cover overheads etc.

I agree with your estimate.

Perhaps also add testing costs in there. With that many components one would have to do some some or all of... flying-probe, automated optical inspection and functional testing. The testing alone would have significant setup costs in the thousands of dollars, that get small when amortized over MANY units (but I seriously doubt there will be more than a few made of these!). Given that this is an actual CPU, functional test is going to be fairly complex.

Really glad that someone has taken the time to do this project, it is effectively a work of art or an interesting discussion piece.

Ah, okay. I thought it 'd be more like a typical PC motherboard with the hundreds of tiny components and iirc a dozen layers.

So basically, when I understand you correctly, a PC motherboard is only as cheap as it is due to scale advantages and lots of the parts on a motherboard being resistors etc.?

Motherboards are cheap almost solely because of scale - they're sold by the tens of thousands, if not hundreds of thousands. They're also sold at a much lower margin (I would imagine). They also benefit from having an in-house production chain, e.g if you're Foxconn you have an entire city working just for you. As a hobbyist you need to pay someone else to make things for you (and pay their salaries +overheads too).

My comment about resistors was that most assembly houses will give you certain components for free because they're an insignificant fraction of the price. Also because almost every digital PCB will use e.g 0.1uF capacitors, they can buy enormous quantities. If you look at the link below you see that most of the cost is in the few specialised parts like the North/southbridge, sound card and connectors.

Here's a teardown and BOM analysis for a motherboard: http://electronics360.globalspec.com/article/3280/asus-p5kpl... . Note the BOM cost is essentially the sale price.

This is partly why Apple's stuff costs so much, because they actually price their devices reasonably (from a business sense). Everyone else works on razor thin margins to give you the illusion that hardware is cheap.

That board would have fitted fine in the old SMT pick and Place machine and solder reflow oven I used to use in around 1998 - 2004.

I think the cost is driven by this being a one off project. That makes one off costs (programming the pick and place machine; profiling the board in the oven; making solder stencil screens; PCB artwork etc) more expensive. I know the costs of these have dropped considerably since I was doing this stuff (2000), but they still add up.

It also means that you don't get economies of scale when buying components. It's usually cheaper to just buy reels of 5000 components than to buy a couple of hundred. (And it makes handling them much easier if you're using a machine to place them!!)