Your profits will be non existent if you keep sending out substandard mugs on an online sales platform such as etsy. Not only from the financial point of view of reproducing and resending orders but also the damage to your account from poor product reviews, even the number of messages and resends that each of your products receives is monitored by etsy bots (it will hide "problematic" listings).
Its not the good stuff which builds an online business, its the bad stuff which destroys it. Stop thinking about "you" and concentrate on your customers buying experience it will pay off in the long run.
* edit . Explanation of last sentence regarding my "you" comment. It is my response to something you said in an earlier post on this thread...."I do individual mugs on Etsy and people just aren't as forgiving or understanding that the flaws are in the mug and not my fault" Is your job to send out a "saleable"mug, not the customers. Why should they be understanding, its not their problem, they just want what you have advertised for sale. Good luck BTW.