The 2004 independent science-fiction film made for $7,000 and featuring time travel is Primer.
Written, directed, produced, edited, scored, and co-starring Shane Carruth, Primer follows engineers Aaron and Abe as they accidentally discover a way to travel through time. Its story is deliberately difficult to follow because the characters themselves struggle to understand the consequences of their invention.
Carruth's background in mathematics and engineering shaped the film's technical dialogue and austere approach. Production took place around Dallas over five weeks with a skeleton crew of five. The tiny budget required limited takes, careful use of Super 16mm film, and the participation of friends and family in several roles.
Primer is often confused with more accessible time-travel films such as Timecrimes or Coherence, but its defining combination of engineering realism, overlapping timelines, and homemade production makes it distinctive. It won the Dramatic Grand Jury Prize at the 2004 Sundance Film Festival and later developed a strong cult following.