The cost of your ads on Facebook is up to you. You can choose between a daily or a lifetime budget, as well as a cost per thousand impressions bid (CPM) or cost per click bid (CPC). You'll only pay for the clicks or impressions you receive, up to the amount you set for your budget, and can view the cost of your ads in real time from your ads manager.
Setting a budget for your ad:
◾Set your budget when you create your ad in the Campaign, Pricing and Schedule section of the ad create tool.
◾To create a daily budget, select Per Day in the Campaign Budget field and set your daily budget amount. You can run this campaign continuously or choose a start and end date.
◾To create a lifetime budget, select Lifetime Budget in the Campaign Budget field and set your lifetime budget amount. You must select a start and end dates for your lifetime budget to be paced across.
Choosing a bid for your ad:
◾Set your bid when you create your ad in the Campaign, Pricing and Schedule section after you select your budget in the ad create tool.
◾We recommend you use optimized bidding, the default option, which will create a CPM bid designed to help you achieve your advertising goals while avoiding advanced settings.
◾For more control over your bid, select Switch to Advanced Pricing and set your goal to optimize for clicks or impressions or set a max CPC or CPM bid.
Viewing the cost for your ad:
◾You can view the cost of your ads once they’re running at any time by visiting your ads manager.
◾In ads manager, select your campaign to see the total cost of all the ads in your campaign.
◾Each ad in your campaign will display the average cost you're paying per thousand impressions (CPM) or per click (CPM), as well as the total cost and cost per action for these ads.
◾The default date range in this view is the last 7 days, but you can change this by selecting a new date range in the upper right corner.