Many advertisers view Facebook "Likes" as a success metric. Of course, the desire for likes is only natural. You want validation that the content you're creating is being received well by the audience viewing it. More likes means you're doing a better job, right? So, they'll spend thousands of dollars building up these Likes, and eventually arrive at the point when they need to calculate their return on investment. While it may look good on your page, it may not look so great as it applies to your core business goals. Beyond that, advertisers across all industries have witnessed a drop in organic reach over the past 18 months. Further calling into question the point behind all these Likes..
So, what is the value of a Like? Well, HubSpot actually made a calculator to help you quantify this at valueofalike.com. Finally, some math behind the thumbs up! And this is to your benefit. It obviously wouldn't make sense to keep spending time and effort on a metric that isn't rooted in actual business outcomes. While this allows you to more precisely understand the value of your Likes, we can get even more granular.
Facebook gives you the ability to create an audience of page fans, and serve paid ads to them. After doing so, you can calculate your return on investment from fans, by determining if they convert at higher rate, or for a higher value than non page fans. Of course, you'll also have to equate for the cost of acquiring these fans if you paid to get them in the first place.
There are other factors you'll also want to consider when calculating the value of a like. For example, you can also serve ads to friends of page fans. A friends name will appear alongside your ad stating they like it as well. By adding this social context to your ads, your fans are indirectly cosigning for the value of your page, which often leads to increased engagement.
Additionally, you'll want to make sure your page fans aren't liking every page they come across. If this is the case, you can expect a decreased level of engagement, and conversions from this audience. In order to do so, check your Audience Insights report in Ads Manager
On a final note, turn and run away from any company that offers you a certain amount of likes for a flat fee! These are not genuine likes, and won't provide any value to your business.