Even I have exprienced very low ecpm in Rewarded Ads, It would be nice they can fix this.
How can be it lower than interstitial ads?
This image is taken from my admob account. Match Rate was 100%. Rewarded ads should give much higher ecpm.
Interstitial Ads - Match Rate 100%
I have noticed that our ad units are not serving any video ads. It is restricted to Text and Rich Media. I don’t know the reason but GAM’s help suggest changes in line item. Set up and traffic rewarded ads for apps - Google Ad Manager Help
Big Companies/Brands are working with GAM, match rate should be much higher.
It will be helpful, if @Diego kodular can reply.