what was the layout of the prime cost of early 8 and 5.25 inch hard
drives? From Seagate and competing manufacturers? BOM Cost and retail
margins (including relationships with dealer networks), R&D costs and
financial burden ...
While it may be interesting to those studying manufacturing economics in the 1980's, I don't think that breaking down costs in such fine detail has much relevance to retro-computing. With the technology advancing rapidly the ratios of R&D, material costs and labor etc. were in constant flux.
However I do know of one case where calculating it should be easy - MiniScribe.
In January 1987... the cost to produce those drives that did sell was
higher than initially thought, which, if properly booked against
sales, would mean their operating margins would be unimpressive.
Instead of reporting this, a number of the managers decided to cover
it up with various means...
This led to the company's most infamous cover-up; the managers rented
a second warehouse in Colorado, where they personally packed 26,000
bricks into hard drive boxes and shipped them to Singapore in order to shore up the inventory count. After the count was complete,
they recalled those serial numbers as defective units, but instead of
writing them off, they checked them into inventory, along with other
failed drives that had been returned