On Sat, 02 Feb 2013 10:37:32 -0600, Swingman wrote:
That's 30 minutes for ALL the project tenons ... Now tell me how long
would it take you to cut 80 tenons in the ends of 40 chair components?

Ok, maybe you can make them that quick. But, there's other factors to
consider too. Setup time, clean up time. However you want to lay it
out, there's always other things to consider too.

Your carpentry pays for your living and your time is often not just
leisure time. Making loose tenons compared to buying them is not as
simple a comparison as it sounds.