I think that Sales Drop is caused from multiple reasons. Some of them can be:
- Launch of Envato Elements;
- Envato stopped advertise on Google(not as it did 6 months ago before sales drop);
- Items Influx -1 year ago, on WordPress category were accepted 25-30 themes per week. Now +130-140 themes per week gets accepted(You can check with archive.org/web )
- Author-Driven Pricing - (ADP)
There is a bigger post regarding Sales Drop issue here: What happened to sales?! ( Sales Drop? )