On the other hand there's no reason why the customer couldn't load the value after arrival and just pay you for a blank coin (has address+key), removing that whole process from your workload.
There is a reason, and it's that I don't want zero-value intact physical bitcoins in the wild. Otherwise nobody can trust on sight that when they receive one, that it actually contains a bitcoin. They would have to look it up, which defeats the purpose of having a physical bitcoin. I realize these are probably going to be collected more than traded, but they still need to remain genuine for them to really have any value. I'd be willing to load them late for customs purposes, but I'm not willing to sell unloaded coins with an intact hologram.
I will, however, sell the Bitcoin coin blanks without the hologram and without any value for 0.15 BTC. I would also offer quantity discounts since I don't have to assemble them.