Depends what you compare it to. If you're looking at the "free" products like Nagios etc, then of course it's more expensive. But Nagios and the like require a lot of time and effort to set up, have ongoing maintance and require their own server (no point installing on the same server you're monitoring).

It's therefore about the value the service gives you i.e. support, ease of use, fast setup, easy alerting (e-mail & SMS) and so on.