They are actually very affordable trailers! Very in line with the regular Jayco and Coachmen types of the same size. I see them on sale from $12-15K on most dealer websites.
Regarding other comments: I have to think aerodynamics matter. I was looking for feedback on how MUCH they would affect me. I would have loved to buy a Tahoe or something that can pull maybe a 20' or so tandem axle comfortably, but realistically could not afford a newer one, and 95% or more of the vehicle's use will be without a trailer so mpg and comfort did matter - and having dog kennels means no pickups. I'm not looking for a luxury full time rig, just a comfortable compact campsite that will keep us out of the weather!
I was thinking probably the difference between a 16' and 18' long trailer couldn't be much, and weightwise even if I loaded 800lbs into the 17FL it would still only be 3100 (i'd be removing the recliner which removes some weight at least) which, with a reasonably aerodynamic shape, should be easy enough to pull? Vs if I add 800 to the 15FK I'd be looking at around 2800, I guess that's not really a big difference.
There are zero tandem axle trailers in this weight range, to whoever suggested that. It's why I end up with tongue weight as my limiting factor, and I've read on these and other forums that single axles can climb up in tongue weight really quickly - that makes sense to me, thus wondering about perhaps the shorter trailer being easier to balance.
I appreciate everyone's feedback, i have been going in circles on these ideas for a while now. Would have loved to find something with a real awning but can always toss a tent up if needed. Would rather preserve vehicle!