Average cost for 100 pages + 100 envelops is about USD $30 (Amazon options). Depending on your printing options, it might double, but that's still well under the same number of greeting cards purchased for about $400.
- Buy some kind of heavy paper that your printer will accept
- Get envelops that represent when that paper is folded in half. So for example, the most common here in the States is "letter" format, which is 8.5x11, so you'd want envelops for 8.5 x 5.5
- Print an image on 1/2 of one side of it
- Write something in the inside flap
1. Setup a new drawing for the page size you'll print to, rotate to landscape under Page - Properties
2. Double click the image to show the orange dots on all sides and click on a corner to rotate while holding CTRL
3. Resize using Draw's ruler to cover one half of the page
4. Add some text and give it some color
5. Save and print
Click on the Page tab and scroll down to the square_right_2 option (basically cuts the page in half). Set the image size to 1100x850 and paste an image on one side. Save and print.
I should note that we have a program expressly for this purpose called "Card Creator" in the database, but I couldn't seem to get it to accept other frame types, even from the options on the official website.
EDIT: Book publishing software might be a little overkill for this, but still a neat idea. https://www.blurb.com/bookwright (untested)
Other suggestions welcome.