The BIG question:  Is Online Marketing and advertising more cost and
time effective than offline mediums? And by how much?

We believe so, but need to demonstrate it to potential clients:

We are needing quotable, verified, and up-to-date facts & figures of
cost comparison between off-line and online advertising using as
example two business sectors:

A - Real estate

	And 

B - Tourism

For example, we have found this report, but cannot verify its accuracy

http://rnacht.realblogging.com/default.asp?item=171156

We would need similar cost comparison ideally for US and European Real
Estat Market, as well as US and European Tourism Trade.

We need proof of the following facts:

1 - Quality Prospect conversion rate.

2 - Marketing and Advertising ROI  and ratio to convert Prospect into actual sales.

3 ? Ration of online and offline potential prospect.

4 ? comparison between:

Organic placement in Search Engines
Internet Pay per click, 
Pay on Placement, 
Direct E-Mailing,, 
e-Banners
Regular Print periodic and newspapers ads,
Off Road banners
Direct paper mail
Telephone Marketing
TV and radio


Wishing you in finding the holy grail argument in favour of internet.

Good luck