My user would have their own customers (say they are an online shop where their customer has bought something from them) and would have some information about them, say name and postal address. They would upload their customer information into my site and the data we have would be used to generate insights or run ML modeling.

Thank you, I was not aware of that. That is very helpful.

It needs a consumer file with demographic, behavioral, and other data. The data set I work with on another project is 600 million records with about 400 columns of data. It costs between $10k-$15k /mo depending on the fields you choose and update frequency. Hosting, managing, and updating that kind of data set also is costly.