Giving back data to clients,

I would like to hear your suggestions and experiences in the following situation:

We provide a software on annual subscription basis to our customers. One of our newly prospective customer asked us about how can they get the data which will be processed/created in the system if they decide to stop using the system.

The data is based on MS SQL Server and according to my analysis, most of the data they might need can be provided in a form of CSV files which is OK I think but I would like to know how to handle the whole process.

Shall we just do it the way: "hey guys send us a list of what you want and we will give it to you" or shall we export the whole db including schemes etc.? What about the whole process, where should we be cautious?

I know that this a lot depends on contract and dialogue but the contract is in progress since it is a prospective customer.

Please, share your opinion, experiences or literature sources like case studies on this. Thanks!