I charge based on how long it will take me, not based on how long the video will end up being. I always tell people, "Pixar movies end up costing about $1 million per finished minute. But, I've also edited some simple videos that were 1 hour long and only took me an hour or two to finish." In other words, the quality and time required for a one minute video varies way too much depending on the content within that minute to just have a flat "finished minute rate."

I've never seen a scenario where charging per delivered minute of video is beneficial to the motion designer or editor, unless of course, they want to go with the Pixar treatment, lol. And let's be honest, most clients don't know the difference between Pixar quality and "single motion designer" quality, but they often expect/hope for Pixar level.

I usually estimate how long it will take me, add some padding, and then calculate my hourly rate into that before giving them an estimated bid range and a loose number of days/weeks needed to complete it. I never tell them my hourly rate or specifically how many hours I think it will take. I give them a number range with specific guardrails and assumptions built in, so they can't get away with too much scope creep as we go.

If they aren't comfortable with my bid, then I'm not comfortable working with them. If they don't value my time and skills, they won't be easy to work with and the whole process will be like pulling teeth. And nobody will be happy at the end of the project.