Sigma Art vs. Cooke Primes: When Do Adapted Lenses Become a False Economy?

Hey everyone,

I'm Omar, a Steadicam op usually working with an ALEXA Mini or AMIRA. I've been eyeing some projects lately where budget is super tight, and the conversation always circles back to optics. I'm seeing a lot of DPs on smaller gigs (think C300 Mark III, FX9) pushing for their own Sigma Art stills lenses, often adapted, to save on rental costs.

Now, I get the appeal of owning a set of affordable, sharp lenses. But I’m wondering, at what point do those cost savings become a false economy? I've heard whispers about issues in post, color matching, distortion correction, vignetting that needs fixing. Or even on set, maybe breathing issues, lack of consistent T-stops, or mechanical limitations for follow focus. When does it actually become more expensive, in terms of time and effort (and therefore money) down the line, to use these adapted photo lenses compared to just biting the bullet and renting something like Cooke S4/i's? I'm genuinely trying to figure out that threshold.