You won't believe your eyes....
http://www.youtube.com/watch?v=NmvYhhyex5U
Yes thats lan with good computer and the server have lanmode on and with settings like:
onfoot_rate 1
incar_rate 1
weapon_rate 1
stream_distance 1000.0
stream_rate 200
I have played sa-mp like this many times with like 5-10 players on Dream Hack the words biggest lan located in Sweden over 12000 persons in one lan.