spend 跟在主语后面可以表达 “花钱” 或 “花时间”,例如：
I spent（过去式）thirty dollars for that T-shirt.
He spends an hour to read the newspaper every morning.
cost（用于金钱上的花费）和 take（用于时间上的花费） 一般都跟在形式主语 it 后面,但也能直接跟在 “事或物” 的主语后面.例如：
It cost me thirty dollars for that T-shirt.
(= That T-shirt cost me thrity dollars.)
It takes me 10 minutes to walk to school every day.
Walking to school every day takes me 10 minutes.
Pay 跟在主语（人）后面,专用于金钱方面的 “支付”.例如：
They paid two thousand dollars for that new TV.
付工资要看语境,pay a salary 或 pay salary 都有可能.例如：
He pays a salary to Mary for helping him to clean his house.
I asked him to pay me my salary by Monday.