It is possible to pay with a debit/credit card using PayPal system. However, having an account or registering for it is not necessary.
Here is how you can do this:
After selecting an answer you are willing to buy, click "Pay", which will redirect you to PayPal website. Choose an option of paying with a credit or a debit card. Continue by adding all the necessary information, agree with terms and conditions, and finalize your payment.