I like your thinking!!! My iMac is about 6 yo, and I have been wondering when it will be time to get a new system, although this still one is still very solid. Agree that those SSD prices are expensive and hopefully will come down soon.
Mac lover here. Still rockin' 2010 Mac Pro laptop and desk tops. Apple likes to see itself as cutting edge, but the really lagged in SSD rollout and pricing. They should have stopped spinning drives as primary storage years ago.
I was shocked when a friend bought a 6-ish yo iMac and it came standard with a spinning drive. It drove like a real dog a month out of the box! He didn't realize he needed to upgrade to an SSD or at least hybrid/fusion drive for that "premium" user experience. Many folks buy Apple because, well, it's just supposed to w*rk!
My OS is only 1 year behind. I think I can run the current OS and even the next one due to a video card upgrade on the 2010 tower, but I'm afraid my ancient application software will protest.
Oh, I can't stand the iTunes software either. Just hope there's a reasonable migration path to something better, or at least different.