I'm used to the fact that first-generation computers were very expensive, which I had always assumed was because they contained large numbers of vacuum tubes, each of which is a rather complex, high precision little machine in its own right. So it's not too surprising that ENIAC cost $487,000, which was a lot of money in those days. According to that article,
By the end of its operation in 1956, ENIAC contained 18,000 vacuum tubes; 7,200 crystal diodes; 1,500 relays; 70,000 resistors; 10,000 capacitors; and approximately 5,000,000 hand-soldered joints.
Which sound like large numbers! So today I tried to find out exactly how much vacuum tubes cost, and found a 1948 issue of Billboard magazine (it's on Google Books, with one of those links that's a whole paragraph long in its own right; are those considered suitable for linking here?), listing prices for several kinds of vacuum tubes at less than a dollar each, including e.g. the 6SN7 which was one of the more important ones for building computers, at $0.75 each. That seems to be retail price in quantity one by mail order; wholesale would probably be less. Say it's $0.50 wholesale. So 18,000 of those would be $9,000.
So what was the other $478,000 spent on?
Other costs of using vacuum tubes, like electricity, and the technicians needed to be constantly replacing burned-out tubes? Perhaps significant, but out of scope here, being operating costs, whereas the above figure seems to be purely upfront purchase cost.
Other electronic components? Doesn't look like it. The only more numerous one in the above list is resistors, and those have to be pretty cheap.
Peripheral equipment like punch card readers? I don't think so. Everything I have read elsewhere says it was considered preferable to use standalone punch card equipment for any job it could do (like keying data onto cards, or sorting cards by sequence number) precisely because it was much cheaper than a computer.
The five million hand-soldered joints? Probably a significant cost, but doesn't seem like it should account for the bulk of it. A quick skim of some hourly wage figures for the late forties suggests factory workers might've been typically paid more than a dollar an hour, say round up to two dollars for total cost of employment. To account for half of the total cost, the soldiered joints would've needed to cost 5 cents each. That would match if it takes 1.5 minutes to solder each joint. It's been three decades since I picked up a soldering iron, and I wasn't an expert with it even then, but that sounds on the high side. I don't think it should take that long.
Inaccurate cost figure, or ENIAC unrepresentative? I don't think so; other computers of the era were even more expensive, for example Univac which ended up costing over a million dollars.
Difference between manufacturing cost and sale price to account for manufacturer profit margin? Okay, that should be a significant chunk of the sale price, but not 90% of it.
R&D cost? That would make sense for ENIAC, but not for Univac, because that ended up selling a total of 46 units, so R&D cost would be amortized to a much smaller sum per unit, yet the unit price was over double ENIAC.
What am I missing?