Why do components cost so much money?

First, not all drivers are equal.  Second, not all crossovers are equal.  Third, Stevdart wasn't being rude - he was simply pointing out one reason commercial components cost more than a DIY solution. 

His point was good.  You can ALWAYS find a lower price in a broadly defined product market.  i.e. in the broad product market "cars" I can always drop down to geo metro from BMW and save a buck. 

Commercial products will always cost more than the sum of the parts.  Even crap products cost more than the sum of their parts.  This happens in every single market in the entire world.  Diet Coke, Burgers, Cars, Homes, Computers, etc.  If manufacturers don't price above total costs they go out of business.  Period.

Why do some similar items cost more than others?  First, manufacturers must meet their costs (advertising, research, development, production).  Some firms use higher quality products, spend more on advertising, don't have the advantage of economies of scale, etc.  Second, manufacturers charge what the market will bear to make a profit.  You don't think they're going to give you the components for no profit, do you?  How can they do this?  Because consumers demand these products.  How can they continue to charge these prices?  Because the consumers pay them. 

I could go on and on.  It might be more fruitful, if you REALLY want to know more about cost and pricing, to buy a few economics books with some pricing chapters.  I suspect you don't really want to know and were simply pointing out that the some raw parts cost less than some complete commercial products.  If this is the justification for DIY you need, I echo stevdart when I say, "go for it!"

Well consider what you are getting. I assume if your going Nakamichi for component sets you're going to get the SP-S6500 comps, and they are great for SQ applications. The reason they are so pricy is observe what you are getting.