Assume that you have an image in the Media Library or in your origin attached to ImageKit. The size of this original image is 1 MB.
Now, you deliver this image via ImageKit and apply different transformation parameters and the size of the output image comes out to be 20KB.
Now, if there are 1 million requests for this final image, then ImageKit uses 1 million x 20KB as the final output bandwidth and bills for it. So, in this example, you would be billed for 20GB of bandwidth.
In your plan, there could be some bandwidth that is included for the fixed amount you pay every month. As long as your output bandwidth consumption remains lower than the fixed included bandwidth, you would be charged the fixed amount as per your billing plan.
If the output bandwidth exceeds the fixed included bandwidth in a given month, then the excess bandwidth (beyond the included bandwidth) is charged at the per unit pricing given along with your plan.
For example, the current Premium plan is at $49 per month and includes 40GB bandwidth. Beyond 40GB, the billing is done at $9 per 20GB.
Here are the billing scenarios
You consume 20GB bandwidth in a month
Your consumption is lower than the 40GB included bandwidth. You will be charged $49.
You consume 40GB bandwidth in a month
Your consumption is equal to the included bandwidth. You will be charged $49.
You consume 65GB bandwidth in a month
Your consumption is more than the included bandwidth. You will be charged the overage pricing of $9 per 20GB for 25GB of bandwidth (the amount that exceeds 40GB of included bandwidth). Since one unit of overage pricing is 20GB, for 25GB you will need two units of overage.
Your bill would be $49 + $9 * (2 units) = $67.
Generally, ImageKit does not bill your for storage. However, if the storage consumption of images, that are explicitly uploaded to ImageKit, exceeds the bandwidth consumption (or the fixed bandwidth available to you, whichever is higher), then you are charged for the excess storage GBs at $10 per 100GB.