It's also important to consider that the difference between Platinum and X3 is huge. Think how much the Linear-Phase EQ, Linear-Phase Multiband, and Adaptive EQ would cost if purchased in the "outside world"...but then when you consider plug-in load balancing, upsampling, Transform Tool, support for all the latest Windows 10 goodies (Pen, Dial, low-latency internal sound chips, etc.), comping enhancements, Lenses, upgrades to TH3 and Melodyne, Theme Editor, new themes, Smart Swipe, tempo detection, Aux Tracks and Patch Points, speed improvements, Rapture Session, synth recording...the list goes on. It really is a new program, as well as a more stable and speedy one.
Upgrading X3 for the past 3.5 years would probably have been about the same as buying Platinum.