We must have saved thousands of dollars on condoms at this point, and intercourse is much more enjoyable for both parties (with no unexpected risk for my career). For some unknown reason (cultural?), while the UID is very popular and obviously the best choice in parts of Europe, there remains some taboo around it in the US... anyway, I wish I could save all this money on disposable products with the cup, but I do not want to risk pulling it out or entangling it.
[1] https://www.nytimes.com/interactive/2014/09/14/sunday-review...
Another method whose safety approaches that of oral contraceptives is cervical mucus tracking. But this also requires education. The method is also not suitable for all women and lifestyles. In one study[1], around 5% of prospective participants had to be excluded due to irregular menstrual cycle. Dropout rate due to dissatisfaction or for other reasons was 9.2%.
Also note that with IUDs there can be spontaneous expulsion, and there are health risks associated with it. So while very good compared to other methods, they are not best in all categories.