I'm the owner of Reliable Response. As alexsolo said, we're an enterprise product, meaning we install on the customer's servers, behind the firewall. Pagerduty looks like a great product for smaller teams or companies which prefer a SaaS solution. Our price point is around $10k, plus yearly maintenance and support fees, so it's definitely geared towards bigger teams.
We have tried to offer a SaaS solution aimed at small and medium businesses.