alt Hacker NewsThey were not made in especially large numbers and they were - look at Ken Shirriff's blog - way more complex than the 8088 chip.
Can't find "good" figures but they were apparently about $100 in 1980 money for an 8088 and about five times that for the 8087, something like that.
That'd be something like $400-odd and $2000-odd in today's money.
I may be misremembering my source (an interview with the 8087 architect lead), but I want to say the die yield on the 8087 was like 30%... just barely feasible for Intel to actually make.