On the website, the products 2265-PX-279-ND and 2265-PX-275-ND seem to have the same specs, but a big difference in price. What is the difference between the two products?
I am including links to the Manufacturers part pages below.
It appears that the difference between these two part numbers are the connectors. The PX-279 has a DB9 connector, while the PX-275 has a D25 connector. If you look on the links below the Manufacturer shows the difference in the two connectors. The DB-25 is a 25 pin male connector, while the DB-9 is a 9 pin male connector.
Manufacturers part pages
8 Port RS232 PCI Express Serial Card 25 Pin Connectors - PX-275 - Brainboxes - Industrial Ethernet IO and Serial
8 Port RS232 PCI Express Serial Card 9 Pin Connectors - PX-279 - Brainboxes - Industrial Ethernet IO and Serial