The cost of an ad ranges based on the type of ad and your location.
If a marketer would like to use a promoted tweet, it ranges from $.50 to $2. The average is about $1.35 per engagement.
For a promoted account the price ranges from $.50 to $4. The average for a local campaign is about $2.35 per follower.
Promoted trends will be the most expensive advertisement. To have a promoted trend, it will cost $200,000 per day