With xDSL you should be able to get pings in the range of 15-30 ms with serves that are reasonable local (I get 23-25ms (6Mbit ADSL) for pretty much any server located in Denmark - with a 10 or even 20 Mbit dsl connection I should be able to do quite a bit better).
And who will prove that it has anything to do with actual tcp/udp rtt?