I would look at DNP event printers. They are designed to crank out hundreds of prints.

The DS-RX1HS can print two 2x6 strips, 4x6, 5x7 and 6x8 prints.

http://dnpphoto.com/en-us/Products/Printers/DS-RX1HS

You can buy the printer and a box or 4x6 paper as a kit, for around $1000.