hello there , first of all hope u the best & u found your needs
i have 2 options for this project :
1- i can extract engaged people data from Facebook fan pages and posts and groups , also ads related to any topic to ur business this would take just 1 day
this will cos u 45$ for the (100 lead )
2- to make a lead generation facebook campaign , best time for any facebook ad should be running for 1 week , during this week i will provide u with the data of people left their info in the ad
and about the cost of the 2nd option this will be based on the type of ur business and how many leads that u will may be needing , but with an average it would gonna be 50 $
MY Recommendation :
is to choose the first one as its will be more effective & cheaper
thanks in advance , and hope u the best