Yikes, good question. Our main concern is that the Show HN thing should present something you've made that exists and works—that it be more than vaporware, a fundraiser or a landing page. I don't think that implies that it has to be free.
That said, users guard the Show HN "brand" pretty zealously. If I'm making the wrong call here, I expect they'll tell us by flagging posts that they think use "Show HN" incorrectly.
Cool. Thanks for that. I wondered why my Show HN was kind of flagged by you. Is it okay if I resubmit it with the link to the iTunes Store to download the App instead of to my website?
I think the problem was that it wasn't obvious that the app exists now. "Coming Q3 2014" suggests it doesn't yet. If it does and can be tried, then sure—either a link to the store or to your website is fine.
We inevitably get some of these calls wrong and are glad to fix mistakes.
To count as a Show HN, there has to be something for people to try out. When you're ready for that, come back and do a show HN then. Good luck!