For the infinite collection you can set your own (higher, midstock level) prices. The images don't have to be exclusive, but they or similars can't be sold elsewhere for cheaper, so that pretty much means only on midstock sites.
Also, they are wanting a higher quality of images for infinite - conceptual stuff, not white background stuff. And they don't want anything similar to what you have in your micro collection.
Which is why it is taking me awhile to get something up. Have to shoot a different concept rather than upload a few from shoots I have already uploaded to the micros.