Photos are the cheap part
A single generated photo costs roughly $0.03–0.10 at current provider prices, depending on model and resolution. Ten photos a week is a couple of dollars a month. That is not the line item that decides your budget.
Video is where the money goes
Video is billed per second, and the price per second is 20–200 times the price of a photo. A ten-second clip lands somewhere between two and six dollars. This single fact should shape your whole posting plan: generate at draft resolution, pick the one clip that works, and only then upscale.
Voice and editing should cost nothing
Text-to-speech at ordinary volumes is a few cents, and local editing — trimming, subtitles, audio mixing — costs nothing but your own compute. Any platform charging you separately per edit is charging for a step that has no marginal cost.
A realistic monthly budget
Daily photo posts plus two or three clips a week comes to roughly $30–60 a month in raw generation cost. Below that you are posting photos only; well above it, you are usually paying for regenerations that a consistent anchor set would have prevented.