No freaking way this is worth $10/mo, especially when creating your own by embedding your Google Calendar in a web page (or in the case of my example, a Google Site page) and sharing the link is free.
The link you provided doesn't accomplish the same thing as their product.
Your link is just a read-only view of your calendar (unless I've missed something). The real utility comes when people can actually schedule something on your calendar without your help.
I've been wishing for exactly this recently, and am excited to try the app.
Also, since I'd use this for work (saving me real time) on a company credit card, $10/month is without question a completely negligible amount.
In summary: I disagree with everything you've said. :)