For a pre-built device I would say it's pretty cheap. Most others are around $200. I've been looking for one myself but can't find anything at a good price either.
Example: https://www.amazon.com/Airthings-2930-Quality-Detection-Dashboard/dp/B07JB8QWH6/
That one is $200 ($300 for the plus version). It's over all much better too.