The verb pay is never followed by a direct object that refers to the thing you are buying. We pay for a product or service:
✗ Credit cards are used to pay the product you purchased without using cash.
✓ Credit cards are used to pay for the product you purchased without using cash.
✗ At that time, very few people could pay a college education.
✓ At that time, very few people could pay for a college education.
You can also use pay in these patterns:
▪ pay someone for something
▪ pay an amount of money for something
▪ pay someone an amount of money for something
It was rumored that Texaco had paid the government over $800 million for drilling rights.
Have you paid your brother for the movie tickets?
However, pay can be used with a direct object which refers to money that is paid for a specific purpose. The nouns most frequently used in this pattern are:
bill, charge, compensation, debt, fine, price, fee, rent, salary, tax, wage
The electricity was cut off after Jennings failed to pay the bill for three months.
Married couples can opt to be taxed jointly, making them both responsible for paying tax on their combined income.