At the top of the pricing page you show that it's $9 a month to have 10 links and enable round-robin call handling, but looking at the FAQs at the bottom, it's actually $9 a month PER USER:
> OnAir costs as low as $9/user/month. This price is per user, per month. Other pricing plans are displayed on this page. Higher enterprise plans are available starting at $250/month for up to 50 users.
This means that for $9, you actually do NOT get round-robin, since you'd need to pay at least $18 (2 users) to benefit from it.
Similarly the 10 links make it seem like you can have links to reach 10 people, but once again this would in fact cost $90 a month.