A major book reseller
puts their advertising on sale
from time to time.
Not all the advertising.
I notice that certain classes
of advertising
are always discounted,
and others are never discounted.
I also noticed
that the advertising
that is NOT discounted
works
(at least, for me).
Authors tell other authors
it works.
The spots sell out.
If advertising works,
there are no need
for sales.
So when you see
advertising on sale,
ask yourself WHY.