What I need:
Simple and cheap way to connect 24-32 plain-old analogue telephones so they can call each other
What I do NOT need:
Calling out to normal telephone network, this is purely separate network for internal comm
Fancy features, VoIP, …
Asterisk running on top of Linux on a cheap old PC seems it would have no trouble handling this but what kind of HW do I need? Most of the solutions linked from the Asterisk site seems expensive for my use case scenario; lots of frills not needed here. $1495 for 4 ports would work out to around 10k$ which is way out of line.