I am playing completely virtual stuff with masterkeyboards and TEC BBC.
The "embedded" PC hardware was some € 1K plus a decent USB D/A.
The software is based on Reaper. The complete cost of course depends on the instrument selection.
Compared to Kemper, I suppose with NT GuitarRig you'll stay below 2K and are a lot more flexible (e.g. you can play in parallel with your keyboarder on the same equipment
).
But believe me, designing and building the system was not for the faint of heart
Another option could be Muse Receptor.
-Michael