While big blockbusters make billions, they also cost hundreds of millions to produce. In terms of Return on Investment (ROI), the most profitable movie ever made is the original 'Paranormal Activity' (2007). The film was shot for a mere $15,000 in the director's own home using a home video camera. After being picked up by Paramount and given a wide release, it grossed over $193 million worldwide. This represents an ROI of approximately 1,280,000%. It beat the previous record-holder, 'The Blair Witch Project,' which was made for $60,000 and earned $248 million. These 'found footage' hits proved that in Hollywood, a great concept and effective marketing can be far more valuable than a massive budget or A-list stars.