we use opensource for many reasons 1st reason it is totally free of charge 2nd with its applications we can replace the hardware with software and we have many examples for that we can use it as firewall like smoothwall,netfilter ,modsecurity and countless of applications.

3rd  flexibility we can editsource and for example we make our own opertaing system and and add features for the operating system.

4th more secured than any operating system

conclusion what we need more than highest performance and lowest cost.