Yeah this one isn’t cheap. I used to have a DS2415+ which unfortunately died on me. Luckily it was during the warranty period and the store gave me a full refund. That’s when I bought the DS3617xs, close to 2 years ago now. It was still a lot more expensive, but with more than half the cost covered by the refund I figured, what the hell. Honestly the newer DS2419+ probably gets you most of the way there, but that didn’t exist yet at the time. And I still don’t like that it only has 4GB.
Please be aware, the DS3617xs doesn’t natively support Synology Hybrid RAID. It supports it if you migrate an existing array from another synology device though (which is what I did). And there is a way to enable it through config file edits. But most users who plan to use that are almost certainly better of with the cheaper DS2419+. Just buy some extra RAM if you need it. It’d still be cheaper than the DS3617xs, which is now getting kind of old as well.