That impression RPM converts to $0.36
Over all my banner impression on Admob I average $0.55 RPM this month.
Some of my apps get higher and some get lower, but that’s the total average this month so far.
I doubt you’re getting a bad deal there.
My thoughts are that your ads probably aren’t that targeted since Wikipedia covers so many subjects.
Reading apps also get lower RPMs in general because users are engrossed in content.
I would suggest optimizing the text colours in text ads and trying out different refresh rates.