To get an idea of how much various components such as CPUs, RAM chips, disk drives and monitors historically cost, and therefore how those costs influenced design decisions that were made, a good source is the ads in the back of magazines like Byte.
There is a caveat: what stage in the wholesale-retail chain did these correspond to?
While it depends on a number of factors, a widely used guideline was that recommended retail price would be about three times manufacturing cost. So if a component cost a computer manufacturer $1, it would add $3 to the retail price.
Taking an example from December 1981 Byte, 16K of RAM (in the form of eight 4116 chips, 200 ns), is advertised for $16. There's no mention of minimum order quantity, so presumably the bulk price a computer manufacturer would pay, was less. Is there a figure available for what the corresponding bulk price would have been?
Or looked at another way: in that year, 16K was quite a common configuration for a personal computer. How much would 16K of RAM have added to the retail price of a computer?
Would the answer be similar for other components such as disk drives and monitors? One data point is the ST-506 hard disk ST-506 price: wholesale or retail? - the answer in that case was that the advertised price was full retail.