Mick Hardy
I've had reports the Humble Bundle edition of Vegas Professional works fine with TandemVids.

Vegas can occasionally be purchased at crazy cheap prices via the Humble Bundle  website.

Vegas Pro Edit 15 was $25USD a month ago. I've subscribed to their newsletter and I'll update this post if they offer it again.

At the moment, it's actually more expensive than directly through the Magix  site.

Unlike the Steam edition, the software is stand alone and does not require a third party launcher so it can still be integrated into TandemVids.