Synthesia sells one thing: a script goes in, a video of a presenter delivering it comes out. That narrowness is the most useful fact about it.
What the plans actually publish
The figures above are read from Synthesia's own pricing page on the date shown, and the full list with links is at the bottom of this page. Two of them are worth reading together: the free plan grants 1,200 credits a month, and the same card translates that into up to ten minutes of video a month.
The field splits on that translation. Descript also denominates a free tier in time; HeyGen meters a count of clips with a one-minute ceiling on each; Runway and Pika publish credits. A credit is a unit only the vendor understands. A minute of finished video is a unit the person who asked you for the video understands, and being able to hand a free-tier output to that person is the difference between an evaluation and a demo.
Where the pricing gets slippery
The Starter card displays a lower figure when the annual toggle is selected, and the toggle state is not always obvious at a glance. The number in the table above is the one shown for monthly billing. If you are budgeting from a screenshot somebody sent you, check which toggle was active when it was taken.
Who should not buy this
If you need generated footage of a scene rather than a person reading a script, Synthesia is the wrong tool and no amount of prompting will change that. It is a category boundary, not a limitation, and the vendor is clear about it.
If you are iterating heavily, ten minutes a month will not survive the drafting phase. That is an argument for starting on the free tier and moving up quickly, not an argument against the product.
What this review does not tell you
Nothing here is a judgment of output quality. We do not generate footage and score it, and we have not found an independent benchmark of avatar realism that we would be willing to rank on. What we can tell you is what the plans commit to in writing, which is checkable, and where the product's edges are.