Clearly you've never seen high power rocketry. For example in the US:

http://www.aeroconsystems.com/Gene_N...balls2006.html

Amateur rocket reaches 93000ft and around mach 3.45.

I live in Australia so we don't have launches with as many people as the US ones, but we still fly some decently high performance rockets. The one I'm building this altimeter for probably won't break the speed of sound and will only reach around 3500-4000ft.

The next rocket I'm planning however will reach around mach 1.1 and fly to around 5Km altitude (around 16000ft).