List the full name of the top five members who spend the most money in the descending order of spending.
full name refers to first_name, last_name; spend the most money refers to MAX(expense.cost)
SELECT T3.first_name, T3.last_name FROM expense AS T1 INNER JOIN budget AS T2 ON T1.link_to_budget = T2.budget_id INNER JOIN member AS T3 ON T1.link_to_member = T3.member_id ORDER BY T2.spent DESC LIMIT 5