Suppliers TS Pharm buys from. The vendor name is stored here once — edit it and it is correct on every product that uses this vendor. Use Products & costs to see and edit a vendor's contracted costs, WAC, % increase, and to import a contract file.
Mass-update vendor costs — e.g. after renewing a contract. Export the current costs, edit the spreadsheet, upload it back. You see a preview of every change before anything is saved.