I really love the idea. I do a lot of instructing, so just as your app is designed to do, I find myself copying/pasting images in to a document and numbering the steps. This is cumbersome in document composition apps because the steps are not treated as distinct units as they are in your app. There's definitely a lot of utility there.
Where I fall off is the pricing. Even at $15/month, I don't think I could stomach it. In my mental model of software, this falls under the category of utility; similar to screencasting software. Tying this to a subscription model, I believe, will be very difficult.
Utilities like this are used to create information that is useful for a very long time. By committing to $15/month at a minimum, you're asking for $180 a year to host a very small set of data, which I can't ever take with me. I think there are other pricing models that would allow you to capture revenue in the utility software market, as well as serve customers who are interested in a bundled solution.
iShowYouHD is a good example. Under their model, I buy their software for a fixed price ($30-$60 depending on version), which I'm happy to pay, because it's great software. In general, I think Mac users are happy to pay for good software, but I digress. Once I've purchased the software, I can record my screen and share the video by exporting it, or automatically uploading to social media video sites like YouTube. The key is, they also provide a "One-click-publishing" option, which I can pay for by purchasing credits. From their pricing page:
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Hosting credits
In order to use the service, you must purchase hosting credits. Hosting credits are consumed in two ways:
1. Storage – You are charged for the amount of data you store per month (on average, calculated daily) at a rate of 24 hosting credits per GB of data stored. e.g: If you store 10GB of data (on average) for one month, you’ll be charged 240 hosting credits.
2. Transfer – Hosting credits are consumed at a rate of 24 credits per GB of transfer. So if use 5GB of data viewing videos, you’ll be charged 12 hosting credits.
Lets say you upload a video 50MB in length. It turns out to be super popular and you have 50 views per day for a couple of weeks. That’s a total of ~ 3.5GB of transfer, or 8.4 hosting credits. In dollar terms that’s just 0.35c (USD). Pretty cheap eh?
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Storage + transfer. That's pricing that fits the product. Obviously, Shinywhitebox sees this feature as a value add for their core product, not a revenue center, but I think you could be a little more aggressive with your credit pricing, turn a profit, and still satisfy customers' need for value.
I would happily pay $20 (maybe even $30-$50 depending on features) for an app like yours, but I'd want the ability to use it without a subscription for a couple of reasons:
* An app like this is frequently used to create a knowledge store; knowledge stores have a tendency to persist for a long time, so marrying my knowledge to a single vendor at what I would consider to be a high price significantly diminishes my perception of value
* Knowledge documents are frequently tied to other products; there is a good chance that I would want to integrate the content created in this app in to an existing website for my own product, rather than having it hosted at a third-party URL
At a very basic level, if the app were able to export HTML and PDF without a subscription, I'd value it at around $15.
With the ability to publish a "project" to a collection of HTML files with some preset/customizable fonts & colors, and I'm feeling more comfortable at the $20 price point.
Create a "Pro" version, that gives me the ability to export single pages or projects/collections using a documented templating system, as well as "raw data" export in JSON with an "assets" folder, and I'm on-board for $40.
Tie in your hosting service at every price point so that I can buy credits similar to iShowU HD, and can "publish" with a single click, and you'll see money from me on a monthly basis as well; just not $15 month :)