OnlySheets: Paywall Your Google Sheets.
Protect your sheets when you sell your sheets.
Share your sheets without having to set your permission level on a sheet to "Anyone with a link". Once deployed, OnlysSheets adds each buyer individually as a viewer to the sheet they buy access to.
Monetize Your Sheets
Step-by-Step guide to integrate with payment processors.
Avoid sharing your sheet with the Internet.
Never have to worry about non-buyers getting access directly from your sheet URL.
More Info at Better Sheets
A google Sheet Template and code.