I am looking for ways to have digital photos printed for public sale at reasonable rates that will allow me to make a profit on the prints. I've seen some very inexpensive prints offered elsewhere that are much cheaper than commercial printers.

For example, I recently saw 5x7's that were mounted on a wooden plaque selling for $16 Canadian. This was the retail price in a gallery shop, so the cost to produce them must have been no more than $8 (probably less). I would love to be able to offer a product like that, at that price, but don't have a clue where to start. Any advice would be greatly appreciated.