That depends on what you are doing and what is your target market..

The question is kinda vague but let me give you some tips..

If you are targeting a mass production / low cost strategy , your profit margin Per Sale is very low, but as mentioned it is a mass production / sale thing , so you need to make sure first you have the large market and reach your break even point, may be after a couple of thousands sale.

If you are selling a differentiated pricy product, your profit margin is really high. But you sell fewer items.

Another important factor, who is your customer ? What is the market segment your are targeting ?

Your production cost ? Shipment ? are you selling a software product for example ( so in this case the cost per unit is negligible ) ? Or selling a physical product ( so you have a cost per item.. ? )

This is a start.. You should look for a detailed analysis after providing enough info.

Reach me if you need more support and good luck !