One of the world leaders in explanimation is Simpleshow, an originally German company that works with fixed cartoons which are swept into and out of vies. Production values are pretty high, and I can see why you would save on all the live drawing, although the format can get a bit bland, as I complain about (jealously) here.
This link is to a nicely done video about their story and vision. The still, where you can see how they work, is taken from that. Started out in 2008, they make around 200 (!) explainer videos a month. They claim to have transparent, fixed price, but I couldn't find any quotes on their website, so I asked. I will post the answer here.