Every AI-generated studio voice in the picker is labeled Budget, Premium or Pro. Budget voices render one line at a time on the studio server, cost the least per line and speak English only. Premium voices render several lines at once, speak many languages and give you the widest choice of voices. Pro voices cost the most per line, speak 29 languages and are the most expressive, with the warmest and most natural delivery in the studio.
The tiers differ in waiting time as much as in price. A Budget run works through your script line by line, and that queue is shared with everyone else in the studio, so busy times can add to the estimate you see. Premium voices render in parallel and finish much sooner. Budget suits short scripts and quick tests; for a full program, Premium voices are the normal choice.
A few Premium voices decline sexually explicit or graphic lines. The studio listens to each newly generated clip and compares it with the line it was given, so a declined line almost always fails on its own and costs you nothing, instead of reaching your track. That check can be unavailable for a spell, and it does not re-examine lines you voiced earlier, so tell us if a track ever plays something you did not write and we will make it right. Most scripts never meet any of this. If it does happen, the two things that work are handing that line to a different voice or softening the wording. Once a voice has declined for you, the voice store marks every voice that runs on the same engine, so you can hand the line to an unmarked one instead. The marks live in the browser you were working in, so a second device starts unmarked. A mark is history, not a promise: any engine can decline, these are the ones that recently did, and a mark fades after a month without another. A declined line is free either way, so trying another voice costs you only the time.
The cheapest sane combination is Budget voices with Split mode: your voices share the script, so every line is voiced once instead of once per voice. Budget with Full mode is the slow one, because every Budget voice then renders the whole script on its own.
Voices are billed per voice, speaking speed and line, so moving the cast to another tier re-voices every line at the new rate; the picker and the synthesis review quote that full price before you commit. Moving back is free for every line you already paid for: each line you were charged for stays credited to your account, on this device and any other.