First, I want total dollars spent by tourists in the U.S. on any kind
of organized tour in a single city, be it with bus, trolley, ferry, or
walk.  I'd like it segmented by city if possible.

Second, I?m interested in narrowing that down and looking at the U.S.
market size for those who take walking tours of major cities.  I?d
like that expressed first with the total number of people who take
these tours annually, whether they pay or not (free example: Freedom
Trail in Boston).  Then, I?d like the total market sized expressed in
dollars.  If possible, it would be nice to have this information
segmented by top walking cities.

Bonus points (and tip) for trend data over the past several years,
average price paid per person for a walking tour, and examples of
annual demand for specific walking tour compnaies.

The total market for US travel and tourism was worth US$441.6 billion
in 2003, having grown by 1.4% since 2002. This information is provided
by Euromonitor International in their "Travel And Tourism in USA"
market survey report. It can be purchased at
http://www.euromonitor.com/Travel_and_tourism_in_USA_(mmp).
Hope you will get everything from that report.