In the heyday of Dynaco, Heathkit, Knightkit, et al, components were individually hand-soldered to terminal strips and PCBs. If you could pass that labor on to the customer, then there'd be money to be saved for the end-user who was willing to wield a soldering iron. But aren't circuit boards in the modern era populated and soldered by machines? Once programmed, the machines can do it forever, and they don't need wages, vacations, sick days, payroll taxes, etc. Furthermore, a kit needs proper packaging -- bags, partitioned trays, etc., all of which may still require hand labor. Plus they need comprehensible instructions, which implies the services of an experienced technical writer. The old days of saving money by doing your own soldering are over. That's the downside. The upside is that electronic audio components are measurably better and much more dependable than in days of yore.