Quoted from their licenses' FAQ:
f however as an individual you make more than $5000 USD in revenue from your Construct 2 creations you will need to upgrade to a Business Edition license. Read more about how license with Construct 2 work.
There is no monthly fee, no annual fee, no licensing per published product or sale you make. You buy whatever license suits you, and that's it. That's what gave me the push to purchase this without thinking twice - of course, other than being the best and easiest HTML5 creation tool - after months of consideration and testing other platforms. Also, like they say, once you make $5,000 from your published creations the business edition becomes affordable enough!
Go wild and publish your brains away!
Hurrr, I'm dumb. I just realized you meant Scirra's own Store! Since that's the case, I'm also super interested in this being answered.