rob8861 - I traded my NC700 with DCT for my 2018 Versys 650. I just wasn't liking the DCT (it's an awesome invention but I just couldn't get used to the way it shifts when I wasn't ready). I really enjoyed the NC700.
LSS - after getting into the adventure-style bikes I bought a used V-strom, then traded for the NC, then traded for the Versys. I initially went to look at a 2016 V-strom but, like your situation, the dealership offered me less for a 2018 Versys! I jumped at it and LOVE this bike!
But I will say, if you enjoy your NC700, minus the back pain, have you looked into different seats? A different seat can make a TON of difference! Out of all the bikes I've owned the ONLY stock seat I ever could ride for long periods was the V-strom's. The stock Versys seat was killing me and I was able to pick up a Sargent seat from a member here on the forum. It's WAY better! (But I still have to do something as my recent 2500 mile trip the Sargent started pinching under my thighs.)
As for pricing, I always say...if you want it, and have the money for it, price shouldn't matter! There's always someone that will get it for way better and others that pay a lot more. But if it's what you want, and can afford it...go for it!
Finally, if you go with the Versys you're going to pay around $700 +/- for bags and brackets. I looked at the Shad's and Givi's but just didn't like the "bubble-looking" cases sticking all out. So I got out the checkbook and went with the Kawasaki side case. (I did get a Givi 47L top case.)
Whatever you decide, keep us posted! Good luck with your decision.