Do any of the cheep ($150) controllers have software emulators?
Not that I'm aware of. The closest that you can probably get would be a USB-DMX interface that offers some degree of standalone operation. Even then, it's usually simple presets at that point and wouldn't take the place of an actual console where one would be needed.
One of the interface companies has a long list of DMX software:
https://dmxking.com/control-software
I'll throw in the
Enttec USB DMX Pro as another widely supported interface. This is what I have and used in my MagicQ PC days.
Can you speak to your needs for beat-activation? Most controllers with this capability are just guessing, as they only respond to various amounts of audio frequencies. Some can "guess" better than others, but it will never take the place of an LD or console operator.