Could Facebook ad engagement be down as prices rise?

According to ad agency TBG Digital, Facebook advertising has seen better times despite it's record numbers of users worldwide. The agency claims that Facebook ad engagement is decreasing as it's advertising prices are on the rise. The large marketing company looked at a hundred billion impressions across marketing campaigns for more than 200 of their clients. Based on their client profile, the price of a thousand impressions using Facebook advertising has increased substantially (41%) over the past year.

What makes this worse is that in past quarter, the agency has seen click-through rates drop by nearly double digits (8%). CPC ads have also risen in the same period.