I think Intel was more concerned about the time it took to make a new CPU rather than the cost. At least that was my impression of it at the time.
That testing is a cost is a given. But it's a known cost compared to what a huge batch of faulty CPU's can cost. Or how about a ruined reputation, how do you even know what that could cost you?
I suppose Intel already use a lot of automated testing, but given all the bugs since the change it seems it is not enough.