Write SQL query to solve given problem: Who is the vendor of the resources needed by the project that had the highest cost of optional tip?. Keep the solution inside sql tag ```sql [SQL-Query] ```
SELECT T1.vendor_name FROM resources AS T1 INNER JOIN projects AS T2 ON T1.projectid = T2.projectid ORDER BY T2.total_price_including_optional_support - T2.total_price_including_optional_support DESC LIMIT 1