What I used to do was to use verotel - Setup as folows. Each movie / clip was uploaded to its own folder with a thanks for purchasing, click here to download page.
I then made that folder just that folder a subset of my main site - meaning I sold 3 days access (enough time to download) to that folder alone, via verotel for $7.99 non recurring. Do each clip in its own folder and you can charge what you want for access to whatever folder you want. All work independent of each other.
Hope that makes sense... I was selling at 7.99 but you could choose $4.99 or whatever you want and each clip sold goes into the same pot (account) so it soon adds up to enough to trigger payout...
Not exactly an elegant purpose built micro-paymet solution, but simple enough to implement and simple enough for the punters to use and pay with
