I'm seeing 3 models on MV charging $25 for solo videos that are around 5 minutes long. I'm not assuming that they're greedy and I know that clip making is a LOT of work. But I don't understand why a model would charge $25 for a 5 minute clip.
Because that's what they feel like charging for their content. There's no hard and fast rules for why some content costs more than other content. It's hard to compare because there are so many variables.