Will (aka Nitewalker) has one of the best videos showing what practical differences you can expect to see between standard gain and SuperGain tubes. https://youtu.be/gFZIlLEci2I?si=K0juTPhnhryUTc-E

It's definitely not a gimmick, because from a scientific standpoint there is a rather large measurable difference in the gain specifications. The reason I shared the video above however is to bridge the gap between that scientific measurement (the difference in gain specifications) with what most people actually care about, which is how it looks to the eye and just how much better they actually perform.
     As far as it being worth the cost increase, it always comes back to what I like to refer to as the "price to performance ratio" (example: Am I paying 20% more $ for a 20% increase in performance?) and then most importantly your use case. I think professionals can always justify paying for any incrimental increases in performance so they maintain that edge in whatever job it is they need to excel in, especially if it involves safety or protection of human life.
    I also know plenty of recreational users who simply enjoy having the very latest tech. For example, I do a lot of night vision photography and can say it's a worthy upgrade for that use case alone.

If you don't have access to try one in person, I recommend looking for as many good video/photo comparisons as possible, and go from there.

Don't forget, it's also not just a higher gain level. All of the TNVC SuperGain tubes are guaranteed to receive the 4um MCP / 3um lead free fiber optic format which is what sets these apart from all of the others on the market.

While not a wholly accurate analogy, the finer MCP can be thought of like smaller / more pixels relative to screen resolution on digital monitors or camera sensors, the smaller the pixels, the greater the detail that can be discerned. This means improved PID, potentially longer PID distances, greater ability to resolve details such as weapons, signage/lettering, facial features, etc.  

The finer MCP allows for far greater potential resolution and detail than attainable with the 5μm MCPs, which raises the ceiling for minimum performance guarantees as well as maximum potential performance.

I'm not wholly certain what information you're looking for, but the P/N spec designation is -24UMH.

~Augee