When I polished the extension with a custom Icon, I went to the Chrome Store with a big smile on my face, it asked me to set up settings, let me set up a custom icon, forced me to think of a good informational text, and at the "moment supreme" of hitting the Publish button it asked me for a credit card. Luckily Mozilla returned that smile and had a suprisingly fast review-proces, it only took around 12 hours I think.
Anyway, now I can first see how popular it will be on Firefox before I decide to try find a 'throw away' credit card.