Yes, when compared to an average fee, it is high.
However, finding a reliable and consistently good PPC manager isn't always easy. Shopping price doesn't mean a better ROI.
Are they managing *only* the PPC? Do they develop/design/optimize your landing pages as well? Are they strictly a professional relationship, or do they have any personal history with other people at your company? How does the ROI compare to that of other Marketing campaigns?
It's not always so clear how certain arrangements came to be. Just make sure to look into everything before trying to renegotiate.