I upgraded Gold to Diamond and it added a year to WUP. My Next upgrade if needed will be Diamond to Horizon + Restoration + Saphira + NLS, right now that's $140 and adds "12" plugins and a year to WUP.
Wup can add value when it adds plugins and/or additional functionality which is never for me. I go the upgrade route instead which adds a year of Wup. Waves customer service is fantastic but you pay for it. If I'm having issues it's usually all of my Waves plugins, I can buy a $29 plugin and be wupped for that.
Once you register it you get 3 freebies as well! It's usually cheaper to upgrade than WUP until the big jump to Mercury, which is way more plugins than anyone needs except @Bapu 🙂