It’s extremely naive to think he wasn’t paid, given facts such as this:

Real Climate blog on Heartland conference
“What if you held a conference and no (real) scientists came?”. Real Climate blog on the invite to the Heartland 08 conference, confirming what speakers were paid ($1000 each) and that their travel and accommodation would also be paid by Heartland.

From the Real Climate link:

The Heartland Institute must have realized that this is not what drives the kind of people they are trying to attract as speakers: they are offering $1,000 to those willing to give a talk. This reminds us of the American Enterprise Institute last year offering a honorarium of $10,000 for articles by scientists disputing anthropogenic climate change. So this appear to be the current market prices for calling global warming into question: $1000 for a lecture and $10,000 for a written paper.