Each item has its own suppliers — add as many prices as you asked for, and tick the one it was bought from. + New supplier
This is saved straight into the Accounts client list, so quotations and invoices can use it right away.
This is saved straight into the Accounts supplier list, so it is there next time too.
Each person signs in with their own username and password. Turning "Cost" on lets that person try the supplier-cost PIN; turning "Active" off signs them out everywhere without deleting their past jobs. Tip: use the same name here as in Team & WhatsApp numbers, so assignments and this account line up.