Pay in gems.
Each image costs what it really takes to make, converted to gems: about 315 for a thumbnail and 250 for an icon. Long prompts and detailed edits cost a little more.
New accounts start with 1,000 free gems, about 3 images. Gems never expire, and you can switch plans or cancel anytime.
$12.99per month
14,000 gems every month
About 44 thumbnails or icons, roughly $0.30 each
For testing variations every week until you find the one that gets clicked.