Advertisement price depends on your decision of what ad type you choose. What are the cost of implementation and maintenance.
Price of targeted advertising
Targeted advertising price depends on how many indicators you take in account for targeted audience.
Price of random picture / text ads
Random picture ad price depends on how many times you wish to show your ad or how many clicks you wish to receive.
Price of youtube video
Youtube video advertising price depends on how long video you wish for your promotion and what quality you want it.