Here is an article from the Reykjavik Grapevine that deep dives on it better than I could: https://grapevine.is/mag/2021/05/07/ask-an-expert-why-is-por...
And for a broader overview, see "Pornography laws by region" on Wikipedia: https://en.wikipedia.org/wiki/Pornography_laws_by_region
There are ongoing debates about how this applies to Onlyfans etc, with one faction claiming all sex work is abuse even if you're doing it solo in the privacy of your own home, so payments to Onlyfans should be banned.
The frame the problem as being vulnerable to escalating customer demands if you make custom content. Like, "insert this object and take a photo, insert this larger object and take a photo, insert this uncomfortably large object and take a photo, insert this painfully large object and take a photo, insert this clearly damaging object and take a photo".