Here is a board ready to use:
https://www.sparkfun.com/sparkfun-lightning-detector-as3935....
https://www.sparkfun.com/sparkfun-lightning-detector-as3935....
Looks like it's steadily increased, labor maybe? Just a WAG on my part to be sure, I'm too far away to legitimately speculate.
lots of products like this are increasing because nobody is running the older cheaper fabs