Unfortunately there's no simple answer. Every business is different and the costs of advertising will vary widely. In fact, at one agency I worked for, we had dozens of SMB clients (think of plumbers, lawyers, contractors, etc.) and we often had two similar business that were down the road from each other get vastly different results. How can two plumbers serving the same area, offering the same services, get such different results and costs?
Two plumbers may seem similar but it's very likely their marketing strategy and assets are very different. For example, if one plumber has a great, mobile-friendly website their traffic from Facebook will convert at a high rate which in turn drives more conversions and better teaches the automated Facebook bid strategy when to bid higher to get a click. Perhaps one plumber is using a retargeting pixel to find people who have already used their service before and is having Facebook spend less on users in that audience. Does one plumber have Video Ads while the other is using Carousel Ads? Is one plumber focusing on Story Ads in Instagram and the other Messenger Ads? Brand Objective campaigns will have very different CPCs than campaigns with the Lead Gen Objective.
Ok, so by now you're thinking. "Are you actually going to help me forecast costs for Facebook or just tell me why it's so hard?!" Well, you're in luck. Each quarter AdStage pulls data from over 6 billion ad impressions across the major ad networks and breaks them down in median costs. So maybe you can't predict your CPC but you can see what others are getting.
For Facebook, we broke costs down for the Facebook News Feed, Right Hand Placement, Marketplace, Audience Network, and Messenger. For Instagram we have two categories, Instagram News Feed and Stories.
On the most popular placement, Facebook News Feed, the median ad cost was $0.81 and that cost has been rising over time.
Instagram Story Ads had a median cost of $1.84 per click and the cost has been a bit of a roller coaster over the past year.
To see how much Facebook ads cost across all ad placements be sure to download the AdStage Q4 2019 Paid Media Benchmark Report.