pay表示付钱,如I pay 10 yuan for this book.
spend花费时间/金钱/精力等,I spent 2 hours on reading the book. She spent 100 yuan on the ticket. He spent his whole life on research.
*pay/spend的主语均为人
take表示做某事需花费多少时间/金钱,如It takes you 10 minutes to walk from here to there.
cost的用法和take非常相似,This book costs 10 yuan.
*take/cost的主语为物
*spend sth in doing...