Buying a Kemper costs a decent chunk of money, so out of pocket cash, yeah, it's not cheap. However, there's another side to this.
I bought some profile packs from one of the highly regarded commercial guys here. It was high gain amps, and cost me something like $35 bucks. In some other thread (I forget where), as a thought experiment I went out and got the price it would cost me to buy each of the heads I'd need to recreate that profile pack. It came out to around $18,000. Sure, you don't get every position of every knob like you do when you buy the amp, but I don't need all the positions. Just the ones that sound good to me.
The way I looked at it for my own purchase was that the pain in my wallet would go away fairly quickly. The benefit of having $18,000 worth of sounds from high end and boutique amps lives on day after day. And that's just one profile pack. I have many others. I also didn't have to spend the $35 since there are 13,000 free profiles on Rig Exchange. So, in addition to the cost of the unit, you might consider total cost / benefits of ownership. From my perspective, it's an insane bang for the buck.
There's another aspect that you should also consider. Modelers like Fractal Axe Fx and Line 6 Helix are a different type of creature than the Kemper. With the Kemper, a profile is a "snapshot" of a miked up amp, i.e. what you hear on the record. Someone a) gets a cool amp and cab, b) mikes it up properly, c) dials in a killer tone and then d) creates that profile. I'm not very good at dialing in tones, so that's a lot of critical work that someone with more talent does for me. With Fractal and Line 6 you can also get great sounds, but they're modelers, so you spend a lot of time in the software building the signal chain from the ground up.
If you love spending hours and hours tweaking, modelers can be a good experience. I don't enjoy that at all, so I press a button to bring up a profile that already sounds great, and just play guitar. I don't see it as one's better than the other, they're two very different things.
I bought the powered head so I can run into both active and passive speakers. Regarding speakers, I'll offer this. It sounds great in my studio reference monitors, so I bought an FRFR cab (DXR-10 in my case). However, before that, I was running (monitor cab off) into a Marshall 4x12 with V30s. Does that sound the same as the FRFR? Absolutely not. So how does it sound? Absolutely awesome. It's just a different shade of awesome.
Those are some of the considerations that I went through in my purchase. I bought it over the holidays so I've only had it a couple of months. For what it's worth, after owning it one week I sold every amplifier in the studio.