Amen to your logic. 6" of scope is still 6" of scope, pleasing views or not, and it's sure a heck of a lot of money to fork over for visual observing. Also, people must consider the appropriate exit pupils that are comfortable to observe with at mid-high powers when the atmosphere allows. I don't care what the design of the telescope is because aperture means everything when it comes down to what can be seen at the eyepiece. I know that a smaller central obstruction makes for higher contrast but that's just common sense. 20% or lower is desireable.
Same goes with selecting eyepieces that don't put 27 additional glass elements into the focal plane to rob light and further diminish contrast.
Again, when you buy a very expensive 6" refractor, you also require a very expensive, top of the line equatorial mounting as well. Seems like a huge price to pay for an exquisite view in a particularly small aperture class. Good grief...
People vary in how they spend their money, and there are certainly many hobbies where folks can spend far, far more than anyone spends on a fine refractor. (Just look at all those boats tied up in any marina.) From a cost standpoint, there is no doubt that the Newtonian reflector on a Dobsonian mount provides the best value for the money. As you say, a central obstruction of 20 percent or less is not worth worrying about. I don't spend much time fretting about what other people spend their money on either.
I think APOs really shine, and make financial sense, in the smaller apertures. You get a nice, portable telescope that provides low power, wide field views unavailable in other instruments, yet it can provide the best possible views at high powers for that aperture. They also double as great nature/birding scopes. Many of them are legal airline carry on size. I've had small, rich field Newts, and they just don't do as well on the sky, and are pretty useless during the day.
Aperture alone does not always determine what you see. Here in upstate New York, where the temperature often drops much of the night, large mirrors always lag ambient air temperature, and simply do not provide good planetary views. The lunar and planetary views through a moderate sized APO, or Newtonian, are far better and reveal more detail.
An expensive APO requires an expensive mount no more than a good Newtonian does. I've seen folks with some very slick and inexpensive mounts for their expensive APO. Of course, if you do put it on a nice equatorial, tracking is a huge advantage when seeking out subtle planetary detail. Any serious planetary observer using a Newtonian really should invest in a good equatorial mount, tracking platform, or computerized altazimuth tracking. (This helps when trying to get the most out of DSOs too.)
There is one area where refractors are unmatched - solar observing. I have yet to see a vanilla Newt set up for H-alpha viewing, or that provides white light views similar to what I've seen through some good APOs.
Aperture and design matter little. It is what you do with the telescope that is important. Any telescope can provide a lifetime of enjoyment, and if you are enjoying the night sky, who cares how much or how little you spent, or what you spent your money on?
Clear skies, Alan