The real answer is, of course, that it totally depends. Here's some reasonable generic ranges though:
SCENARIO CPM AVG ADS/PAGE PAGE VIEWS
-------- ------- --------- ----------
Best $1.00 2 2.5 million
Okay $0.25 2 10 million
Bad $0.15 2 16 million
You can almost always show more than one ad per page. But, don't over do it.The primary way to generate significant ad revenue with low page views is to have highly targeted content and sell ads directly for $4+ CPM. It's better to think of this kind of advertising as sponsorship, and charge appropriately (preferably thousands over month+ commitments).