Billie Ruben wrote up a guide on how to 3D-print sex toys the right way. Just rolling one off the printer and into a human body being absolutely out of the question due to the materials and the layer lines being perfect food and habitats for germs. Using the printed blank as a mold, though, leads to further work and expense. Instead, get some beeswax.
This method is perfect if you want to make custom one-offs, like lots of different/interesting toys. It's also great for beginners! If you've never casted (or done 'organic' digital sculpting) this is the perfect beginner project! I recommend making a day of it, with a bed-fellow or friend! Giggles and fun will be had by all (including, if our experience holds true, the silicone shop owner! 😊😁🤣)