I produced a flyer with a JPEG background and 2 SVG QR codes. The whole thing is repeated multiply in the document, for some variations of the flyer. It would seem that typst reembeds the images for every repetition.
`ghostscript -dNOPAUSE -dBATCH -sDEVICE=pdfwrite` recognised this, and manages to reduce the file size, by a quarter to almost a half, depending on the exact nature of the images. As a workaround this is ok. But it would be great if typst could match this out of the box.