Hi
It's not "normal" to have a 30ms response from a directly connected device on the LAN. Sounds more like you are pinging the LAN interface over the ADSL connection where 30ms is quite normal.
If you are pinging this box from the local subnet, then check what is happening on that box. Check the CPU with the command :-
sh processes cpu sorted
or check the interface for heavy use with the sh interfaces command and check the 5 min input/output.
Do you have any QOS on this box that could be rate-limting ICMP (shaping) perhaps.