I agree with Jeff on the whole hobby / profession median. As for the shipping expenses, I think that is something that we unfortunately have to suck up, and accept as being included with the fee for a reptile. However, for something such as a $20.00 gecko, I believe adding $15.00 or so for time and effort is reasonable, for the obvious reasons. This is of course, my humble opinion.
The best way to find a happy middle point, I would say designate specific shipping dates. For example, depending on how much you sell, once a week, two times a month, once a month, or whatever best fits your individual time frame / situation.
Elementary economics. When supply is greater than demand, the "demanders" can set the price (within reason). And when the demand is greater than the supply, the "suppliers" (breeders) set the price (within reason). Its basic, but it applies. And it applies to snakes and snake breeding.
I was in the middle of typing something surprisingly similar to that. I personally believe that no reptile should be less then $100.00, $75.00 at least. Why? I just cannot justify the life of a living creature for $15.00. In addition, when reptiles can't be purchased with a childs weekly allowance, this filters out those who are, often times, not capable of holding the responsibility. After all, one is much more likely to put effort into something they paid $100.00 dollars, then something they can replace with an additional 20 dollar bill.