Full Answer

It's worth separating the API from everything around it. TikTok does not bill for sending events; the Events API is part of the advertising platform and, like the browser Pixel, is provided so that advertisers can measure and optimise. There is no per-event price and no data ingestion fee. If a vendor implies the API itself has a usage cost, that's a misunderstanding of how the platform works.

Where money actually enters is implementation and infrastructure. Sending events server-to-server takes development effort: mapping WooCommerce events to TikTok's schema, hashing customer data, handling deduplication, and testing. You can pay for that as a plugin, an agency's time, or your own hours, but it's a cost of building, not a fee from TikTok. Infrastructure is the other variable, and it depends entirely on architecture.

If you route events through a server-side GTM container, you pay to host that container, commonly $50-120 per month for a small store. If instead you post to the Events API directly from the WordPress server you already run, there's no additional hosting line at all. So the honest answer is that the API is free, the Pixel is free, advertising is not, and your only structural decision is how much surrounding infrastructure you want to pay to operate.