Check out the National Technical Information Service, which publishes some federal data sets like the SSA Death Master File (https://dmf.ntis.gov). They charge $1,531 per seat per year to do online queries or $2,930 + fees to download. They are exempt from FOIA, but the products are still public domain.

Half of their links are dead but they've updated their website to say:

> We help agencies leverage new and innovative capabilities, including super intelligence, machine learning, and robotics.