Thanks to the folks at Hackaday for their very complimentary blog post on my system - much appreciated. Reading it, two possible questions came to mind:

1. Why are custom systems so outrageously expensive (tens of thousands of dollars)?
2. Given that my system is so simple, why does it even cost $600 to build?

The answer to the first question is easy. These systems are typically built to the customer's specification, which often requires a design unique to that customer. The parts are often not off-the-shelf, but have to be custom fabricated. A high-quality DSLR and lens is often included, which can easily add > $5K to the cost. The design needs to be rugged, the software bullet-proof, and the whole system has to be warrantied by the builder. The builder will typically have to travel to the customer's location to install the system, and train people on its use. Plus there's the overhead associated with the organization that's building the system. It all adds up. Here's one example of a very nice custom system at the Yale Institute For The Preservation of Cultural Heritage, built by Cultural Heritage Imaging:

That's a really sweet system - if I win tonight's Powerball, I just might order one like it :).

Having said all that, one of my systems is capable of producing comparable results to the one above, even if it doesn't look quite as elegant. Which leads to the next question: given that this is just a bunch of LEDs turned on and off inside a dome, what makes it cost as much as $600? Well, here's a list of the most expensive components in the system:

• Acrylic dome - Cost of this depends on size. The dome for the 12" system whose build I'm documenting here cost about $86; an 18" dome for a previous system cost about $135; and so on for larger sizes.
• LEDs - This is the number one cost. I use 3W/1A Cree LEDs on a star heatsink; smaller/less powerful LEDs just won't cut it. As I mentioned in an earlier log, don't cheap out on these - buy them from a reputable source. Chinese websites advertise "Cree LEDs" for less than a buck each in quantity, but the quality of these is dubious, as I found out to my chagrin. Last time I bought these, I paid about $3.30 each in quantity; just checked the price at LEDSupply, and they're down to about $2.75 in quantity. For a 12" system, you'll need 48 (plus a few spares), so that's about $150; for an 18" system you'll need 64 plus spares for about $200.
• Enclosure - The only enclosure I found big enough to hold the Arduino and accessory parts is this one from Polycase for about $14; however shipping kills you at an extra $10. About $15 more for additional screws, nuts, washers, spacers, bringing the total up to about $39.
• CAT4101 LED drivers and breakout boards- You need 8 of these. $2.92 for the chips at Digikey, but since you get a price break at 10, makes sense to get two spares at $2.62, for a total of $26.20. $2.21 each for the breakout boards. Total of about $44.
• Arduino Mega R3 - About $10 for a clone, about $30 for the brand name board.
• Kynar AWG24 wire - $23

So for a 12" dome we're already up to about $370, for an 18" dome about $470. The remaining parts are pretty cheap, so the total should come in at about $100-125 or so, and that's where the "about less than $600" figure comes from. If you can find these parts cheaper, let me know - I'll add links to the components list.

You could design and build a system with lower-power LEDs at a significantly lower cost, but then you have to deal with substantially longer exposure times even for small domes, and impractically long exposure times for large domes. My first dome started out with 0.5w/0.1A LEDs, and was painfully slow; the next iteration at 1W/0.3A was still pretty damn slow. 3W/1A LEDs are the way to go, even they cost more upfront and complicates the design. Even higher power would be better, and I may look at that for future iterations. But not now.