I guess it depends on how you typically use the amps, IMO the Kemper is quite far from the experience of using the real thing. I made lots of Kemper profiles of my Herbert before selling it, as well as ToneX models. Even though they sound very much like how I dialled them in, the experience is totally different. It’s not really a substitute IMO.
The STL, Brainworx, QC and Fractal models all give a pretty good experience of what the amp is like to use controls and layout wise. But even with those, I think you’d just be left wondering what the real thing is like until you hear for yourself.
Amps are for sure expensive, but if it’s a sound you really love and/or need then it’s worth aiming for. Someone who is looking to buy a £200 pedal is likely comparing against other options in that price bracket rather than as an alternate option for an amp. The good thing with the real amps is they hold their value pretty well. There tends to be better deals on Diezel in Europe than we typically see for Bogner/Friedman/Soldano etc too, I paid £1500 for my Herbert and I’ve seen VH4’s go for around that too.
Tbh if you love the pedals and models of it, it’s worth the punt in trying the real thing.