this might just be true. admissions is expensive to run, and the secondary fees of all the rejected people subsize the interview days and the overhead necessary to process the rest.
it surprises me actually that more schools aren't exploiting the fact that increasing their secondary fee has a negligible effect on application volume. Dartmouth's fee went from $85 last year to I believe $130 (?) this year (College-wide budget cuts) Do you think their app volume went down? I sincerely doubt it.
What's impressively wasteful though, isn't the emails. admissions spam costs nothing to send out. It's when you get full-on 11.5"x9" manila envelopes (the kind that cost like a dollar to send) from schools at which you just have no shot b/c of horrible fit. CCLCM, I'm talking to you