(I am not affiliated in any way with Fractal Audio).
Taking the Double Verb as an example:
https://shop.fractalaudio.com/dynacab-pack-2x12-double-verb/. It's $29, so on the lower side price-wise. You get:
- Condenser 023 based on the Soyuz™ 023 BOMBLET™
- Condenser 87 based on the Neumann™ U87
- Dynamic 57 based on the Shure™ SM57
- Dynamic SM7 based on the Shure™ SM7B
- Ribbon 313 based on the Shure™ KSM313/NE
- Ribbon 121 based on the Royer™ R-121
What that means is that you can adjust the tone for that Cab almost as if you were moving around any of those mic combinations in the real world. If you are the type of person that can really hear those mic'ing differences, and you know (or want to experiment with) these particular mics then it is probably worth it.
On the other hand, if you have a specific tone that you already know you can get for a specific Amp using a Cab IR taken from an original 'Verb (or something else that you feel is a great combo), and you're happy with it, the specificity of this DynaCab pack is probably overkill.
If you shop around for IR Packs, you'll find that they are similar prices (most of the time for the decent ones), sometimes more. Each time you preview an IR you have to load it, which isn't really a massive deal, but if you're a tweaker, DynaCabs really do take some of the tedium out of that process, and as I said, you're getting a more "real world" experience, which helps reduce the time spent getting the tone you want, especially if you know what you're doing.
As a final thought, it's worth looking into some of the alternatives to DynaCab like STL Ignite Libra (see link below). They don't work in quite the same way as Cab Lab in that they don't "understand" DynaCabs for example, (which are Fractal proprietary tech), but they are powerful and the better ones give you a lot of scope for working with the balance and orientation of IRs (plus a whole bunch of other things). You can pour a lot of time into this sort of thing like all this stuff though, so it ultimately depends on what you enjoy doing, and what you're trying to achieve.
https://www.audiopluginguy.com/apg-guide-to-guitar-cabinet-ir-loaders/
To that list I'd also add Cabinetron, which is cheap but quite powerful.