The plugin from the link sets the player's money to 0 and uses a fake message to display a different amount in the bottom-right corner that cannot be retrieved with cstrike.inc's money functions.
Try replacing every instance of sending the "g_MsgMoney" message in the .sma like this:
Code:
message_begin(MSG_ONE_UNRELIABLE, g_MsgMoney, _, id)
write_long(zp_cs_player_money[id]);
write_byte(1);
message_end();
To:
Code:
emessage_begin(MSG_ONE_UNRELIABLE, g_MsgMoney, _, id)
ewrite_long(zp_cs_player_money[id]);
ewrite_byte(1);
emessage_end();
Just add "e" in front of every function between "message_begin" and "message_end".
The difference between "message" and "emessage" is that the latter can be detected by other plugins.