Hopefully you have a maximum width / maximum height set up in your permissions so that the very large images get resized down to a much smaller size. That massively reduces the file size. So the 9MB image will hopefully become < 1MB if you're resizing it on upload.
That will also need the maxImageResizePixelCount
config option increasing as above but as long as there are no memory limits being hit, the resulting file should be much smaller.