Well, one usually understands better the components if one reads the datasheet...
Let's see:
The chip is a Stratix 5SGTMC7K2F40C2ES FPGA:
28.05-Gbps and 12.5-Gbps transceivers ( 150 + 36 )
Backplane works up to 12.5-Gbps data rate capability
I/Os are 1.4 Gbps LVDS (each pin of the 600 I/Os)
On chip termination included
Memory interface at 1066 MHz included
The 600 I/Os do not include the 186 transceiver pins
Hardware already included for 10 Gb Ethernet and many types of PCI-Express interfaces.
2560 blocks of ECC Memory of 20 Kbits each
939K registers
512 multipliers (18x18 bits)
256 multipliers (27x27 bits)
For data (or voice) networking equipment, if you need to route, filter or "collect data" from a BIG, BIG amount of traffic, there is nothing like an high end FPGA.
It is "normal" that the price is also high-end.