Not Quite Erik,

The toaster ovens are used to assemble SMT boards, and it works quite well for prototyping (smirks and snickers notwithstanding ;)). This, of course, has no impact on the number of layers in the board.

And while most people can etch a single layer board in their sink, multi-layer boards become a problem without some special equipment. In order to make two or more layers on a circuit board, you need to be able to plate the holes and vias. Yes, if you have few enough holes you can make a two layer prototype by hand soldering the holes and vias instead of plating them, if you can control the registration. But in any professional application, or any application where you need to know how the mass produced boards will function, you need to plate the holes even on a two layer board. And if you can make a two layer board, you should be able to make a four or six layer board with no problem, just by adding the ability to laminate prepreg. Eight layers start getting tricky. Then you have to control the registration in spite of the lamination forces required, and plating the high aspect ratio holes/vias requires special equipment.



That's not a bad analogy. The issue is the manufacturing setup. Board shops are set up to process panels, not boards. Panels (in the US anyway) are typically 18" by 24". When a board shop quotes a job, they calculate the number of panels they're going to make, not the number of boards. They then convert the price into a "per board" price. On top of this is the NRE (Non Recurring Engineering) cost. This is the cost of making the films, master and working, silkscreens, laying out the panel, etc. This is usually reflected in what you phrased as "$100 to start the machine."

Anyway, the shops that advertise "$40 per board" are counting on getting enough orders to fill up a panel with different jobs.