The "Forecast" column in my Billing and Cost Management console predicts an unexpectedly high bill for me. Why is my predicted bill so high?
Most AWS services bill on demand, meaning that your overall bill steadily increases over the course of a month. However, some services or features bill a larger amount at one time, usually on or near the first of the month.
Because your average daily cost is higher at the beginning of the month, your forecasted usage for the rest of the month might appear to be higher than you expect.
As the month progresses, the forecast is a more accurate prediction of your final monthly bill.