Stick a pin in it

My various pin badges (exhibit A, exhibit B) keep loosing their back holder. Luckily I haven’t lost an actual pin yet but before I do I bought these rubber ones instead.

Now that’s not very interesting I know. What I find interesting is that I got 25 of them, from China, for $1.90 (just over a pound). How is that possible? I just had to wait a few weeks for it but that’s fine. How can something be so cheap, including postage?!