That with my (conservative, I believe) estimation would make 6-9,000,000 US$.

Let's make it 10,000,000 US$, that were "wasted".

Sending 200-300,000 of such mails makes no sense whatever, AFAICT a study (besides the ones with 12, 18 or 33 participants), if the sample is random enough, with 1,000-10,000 should give accurate enough results.

In the good ol'times (snail mail) sending 200-300,000 letters would have costed probably 200-300,000 US$, I doubt that the Uni (or its IRB/whatever commission) would have approved this kind of expense.