Complete newbie here - where do I get PlayHT API credits without a subscription?

I've been evaluating various TTS APIs for a benchmark series on inference cost versus output quality. PlayHT is on my list, but their pricing model has a point of confusion I need clarified.

Their documentation and dashboard heavily push the subscription plans. For my testing methodology, I require precise, pay-as-you-go API credits to measure cost-per-request. Subscriptions with monthly allotments introduce too many variables for a controlled comparison.

From my analysis of their site, I see two potential paths, but need community verification:
* Is there a direct "API Credits" purchase option buried in the billing section that isn't advertised upfront?
* Does one of the lower-tier subscriptions simply function as a non-recurring credit pack if you cancel auto-renewal immediately?

My requirement is straightforward: a way to purchase a block of credits (e.g., $10 worth) to use solely via the API, without an active subscription's monthly voice generation limits. Has anyone successfully configured this?

For context, my standard test uses a script like this to measure performance:

```python
import requests
# Example API call structure
response = requests.post(
'https://api.play.ht/api/v2/tts',
headers={"Authorization": "Bearer YOUR_API_KEY", ...},
json={"text": sample_paragraph, "voice": "voice_ID", ...}
)
```
I need to know how to fund the account that `YOUR_API_KEY` draws from. Any insights from those who've navigated this would be invaluable for my benchmarks.