Spec' Tarmac (road), Ridley Fenix (commuter & fast tourer), Salsa Mamasita (MTB), CoMo Speedster (tandem), Surly Big Dummy (cargo), Airnimal (folder)
Your question is pretty vague. The $600 tandems are close in quality to the cheapest single bikes, although maybe a tiny bit better than those. Whether that will be suitable for "recreational riding" depends on what you mean by that vague term. You may find more options in between the two price ranges if you look for a used tandem, but getting one the right size can then be a problem.
Rans Rockst (Retro rocket) Rans Enduro Sport (Retro racket) Hase Kettweisel Tandem (redundent recumbent), Merin Bear Valley (The gopher).
I think that most of the difference is in the frames. When I had my own bike store during the late 90's I kept 3 tandems in stock: an entry level ($600)Univega or KHS, a mid level ($1,200) Burley and an upper level ($2,400) Santana. It was instructive to ride one immediately after the other. Riding the entry level bike after getting off of the Santana, even around the parking lot, would feel so flexi it was scary.
You didn't say what your bicycling background was. If you're used to riding better quality bikes I doubt you'll be happy with such an entry level tandem.
The best bang for your buck would tend to be a good used name brand tandem. The Schwinn name is not what it used to be. I would advise looking for Santana, Cannondale, Burley, Trek etc.. These can be had in good working order for $800 - $1500 and will generally hold that value for some time so they can be re-sold later if you decide that tandemming is not for you. A $600 entry level Schwinn will be worth that for aproximately one second beyond the time your credit card is debited.
I think a simple measure is what kind of single do you ride? If you ride a $300 single then a $600 tandem might make you happy, but if you ride a $1000 single then a $600 tandem is going to feel pretty crappy. In our case the tandem is our "high end" bike, where our singles are middle of the road hybrids from the LBS. When I ride my single now I notice the difference in quality between the two.
Nishiki Continental, Bilenky custom travel tinker, home built winter bike based on Nashbar cross frrame
Given that extra information, your choices are basically "most" of the used market for any of the name brands. I was able to pick up a used Santana last year, for something in the lower $1000s, which I managed to keep below $1900 by the time I replaced the brake shoes, one of the brakes, the captain's stem, both sets of bars, and the brifters. Most of these were replacing what didn't work or fit. If you're interested in new, consider the Hokitika made by Tandems East in NJ (it only sounds like it comes from the far east).
In addition to what you found there are a few even cheaper models out there, and a small number of folks have been happy figuring they were buying a frame and didn't need to replace all the components - only some of them. But these come only in one size.
If looking at new, consider pricing a single bike with the same grade of frame and componentry as you would be happy riding. Expect to pay MORE than double that, but probably not more than triple. The tandem-specific components more than make up for the reduction in quantity of a few components in price.