The Value optimization helps marketers target the most relevant groups of potential and existing customers for their campaigns, giving them more efficiency and value from the advertisement. We will probably concur that the most relevant customer is the one which brings the highest value to your business. 

This optimization type works based on the purchase values sent form the Facebook Pixel to estimate how much money someone may spend with your business over a particular time period - 7 days. The ad's bid is then automatically adjusted based on this estimation, allowing campaigns to deliver ads to people likely to spend more with your business at a low cost.            

To make this happen,  you should add a 'value' to your conversion code by modifying the Facebook pixel code. When you add a value to your pixel you can report your return on investment in Facebook reports. If you would like to report a value in a currency other than US Dollars make sure you also modify the 'currency' field in the custom data.

To sum it up, the pixel, SDK or your product set (depending on the objective you want to use) has to:
■ have 100+ attributed purchase-optimized conversions per the last twenty-eight days(This is the minimum threshold at which we have confidence that an advertiser should benefit from value optimization.
■ send a range of distinct purchase values (at least 10 per last twenty-eight days)     - Businesses that have only a few products/price points or send static purchase values may not see a large lift with value optimization. 

Note: For Product Catalog Sales (DPA) objective: Your Product Set must also meet the requirements above.
​
​Most common reasons for ineligibility:
​○ You have fewer than 100 attributed purchases (last 28 days)
○ You are not currently optimizing ads for Purchases
○ You are not currently passing back purchase values
○ You are only passing back a few (less than 10) distinct purchase values

Keep in mind that eligibility kicks in with a delay of approx. 1 week because Facebook determines attributed conversions based on a 7-day conversion window. 

If your ad account has been already permitted to use the value optimization by Facebook,  you can use also Value Optimization with Minimum Return on Ad Spend (ROAS) bidding. This option lets you set the lowest acceptable return on ad spend, giving you more command over the value a campaign accrues to your business. After establishing a minimum return on ad spend, Facebook will adjust your bids to deliver a return of at least that value or more over the duration of the campaign.