DataCircle - Sharing Data
"Find, Buy, Sell and Exchange Data Sets easy"
"DataCircle is a data exchange network where you can find, buy, sell and exchange datasets easily. It is great for researchers, educators and students—there are more than 50 dataset categories... DataCircle is also dedicated to helping open communities—there is a free tier to use, share, and exchange free data assets."
There was a similar (purpose) service "Microsoft DataMarket" available on Microsoft Azure, now being retired
The actual viable data market is Kaggle, now owned by Google.