How much do tourists to Asia, Africa, Middle East and South America
spend every year on hotels, tours and rental cars (not flights)?

I wouldn't discount the figures yet.  From this site, It seems that
one can gain insigh:
http://www.world-tourism.org/facts/menu.html

But one would have to buy the one or other book that gives details of
the methodology to find out.  Here is what the "overview" on that site
says:

"NWTO also provides the world's most comprehensive tourism statistics.
Member States, private tourism companies, consulting firms,
universities and the media all recognize UNWTO as the world's most
comprehensive and reliable source of global tourism statistics and
forecasts. Tourism data collected from 190 countries around the world
include: arrivals, receipts, overnight stays, mode of transport,
length of stay, tourist spending, and origin of visitors."