From the FAQ:

> It costs our tree planting partners about 0.22 EUR to plant a tree. 22 cents divided by 0.5 cents makes about 45 searches until we can plant one new tree.

This charity focuses on tree planting and this page has a breakdown on the costs a bit down the page: https://onetreeplanted.org/pages/about-us

When I planted trees I got around $0.25 per tree. Some of the other companies paid as low as $0.09.