It really depends on it, as with all domains.
If something is off just a tiny degree it can make the value go from millions to zero in less time than it takes to snort in derision.
mp3.org would be worth a lot, np3 or jq2 not.
Generally speaking, mixing letters and numbers is never good unless everyone knows what it is supposed to be anyway.
The most famous exception to this rule is mp3.com