Have you considered SharePoint 2010 for internet sites license?

In MOSS 2007, to run a public internet site on SharePoint included many hidden costs that soon accumulate to a big number that puts it out of the reach of most small and medium companies.

As a rough calculation - it costs over $160k to run 3 MOSS servers with internet license for internet sites.  As much as people loved the features of MOSS for publishing sites - this was a major drawback.

Microsoft recognized this problem, and in SharePoint 2010 line up, they added an additional "SharePoint 2010 for Internet Sites" licenses for standard and enterpise features. 

Microsoft has yet to release pricings for SharePoint 2010 - but we can expect the internet sites for standard SharePoint Server to be highly comparable.