There is at least one source that is fairly reputable. That is the RV Consumer Group 'Green Book--RV Ratings" for 2003. They show selected Airstream models with suggested MSRPs. These figures were derived from their research, but always seem pretty accurate to me.
For instance, here are a few of the quotes from pages 123-125 of this year’s edition:
A/S Classic, Classic 25' $51,707
A/S Bambi, Bambi 19' $29,547
A/S Classic, Classic 31' $60,149
A/S International, 22' $39,044
AS Safari, Safari 25'A $36,934
You can get this guide by going to www.rv.org.
It is not the only source, just one. fyi
99 25' Safari A