I think we are basically saying the same thing, we might just be using 'low end' and 'truly fine machines' a bit different. I am not familiar with most of your bikes to see if they are low/high end or truly fine or whatever. My sub-$100 LeTour is certainly not considered a 'truly fine machine' by any bike enthusiast around here and I'd call it just about the bottom of Schwinns lightweight road lineup (I do not even consider rec and department store bikes like varsity in the low to high range, they're simply not even included in conversation). Only the Traveler and World Sport were below, and about 10 models above it IIRC. However I'd say its a great bike, as good of ride as any other I have rode and if it was my only one I'd have no reservations about upgrading it. Lots of happy Traveler owners out there too, for that matter.

I put quite a bit of money into my old Tempo. It sits in the middle of Schwinns line up, and cost me a little over $100 originally. Still, certainly no 'truly fine machine' by most standards here. I threw Campy and Dura Ace on it, and nice light wheelset too, and it's great. I probably went overboard, with maybe close to a grand into it, but I love how it turned out and the nice parts can always be taken back off later. I'd take it any day over a new 1k bike.