Correct price communication?

I wanted to buy a wp theme for $ 29. I registered an account and bought 30 credits for $ 30. I started shopping. It turned out that the total amount of the bill was $ 37 and not $ 29. They asked me to buy at least 20 credits for 20 Dollars so I could pay the original $ 29 for the original $ … and so $ 50 for $ 29. Congratulations it is so tirelessly incorrect! I buy and hope to contribute to Envato’s development because it is in need of it. I guess there is no way I can pay the exact amount of money with my card or get the 30 credits and buy credits again but only for $ 40 …?

If you haven’t spent any of the credit then you can try (no guarantee) to submit a refund request and get the credit returned then use a direct payment method e.g. PayPal which means you pay the actual amount (potentially plus a small handling fee where required)