Working on a background page for my IEEE-754 project, I looked up the history of the Intel 8087 coprocessor (the origin of the IEEE-754 floating-point standard), and discovered that it had 65,000 transistors, and sold for about $150. Since “shave and a haircut … two bits” puts the value of two bits at 25¢, and you can store a bit of information using one transistor, that would put the cost of the 8087 at less than .02 of a bit per bit.