I could use a cheaper sending option and that would really boost the profit. That would introduce an initial delay for the subscription start, but of course after that it would not be noticeable for the subscriber.

One time I was experimenting with sending first package using airmail and subsequent packages simultaneously using the cheaper shipping option that was supposed to be 2 weeks slower. But in reality the slower one arrived first and the faster one a day later, leaving subscribers confused.

Try switching a quarter of your subscribers to it and see what the reaction is. If its not bad, move all of them over.