So you believe that the limit was successful calls? I'll accept that, but do you think that it is a cost issue? Again I'm no statistician either but that seems to be a strange limit. However, I understand that there many be a valid reason for this criteria.
In order to reach a specific "error rate", such as +/- 4%, there is a specific number of individuals that you need to poll. Once they reach that number, it doesn't make sense to continue to call, unless they want to try for a lower error rate. And cost is definitely a factor.
I was called several months ago for the Rasmussen poll. It is totally automated, i.e. computer driven. I don't think that Time and Newsweek and others use this technique.
There are arguments pro and con. For instance, how many teenagers are answering the Rasmussen poll? With a live poll, the person taking the poll can make judgements that the computer can't.