For most people:
AltMonkey = any con higher then myself
I have been called AltMonkey when flying at 8K, and I have been called AltMonkey by cons flying at 25K who just happend to be 2k below me
There are many reasons why people fly that high: Cowardice, not yet knowing what's a good alt to be at, using the strenghts of a plane (not everybody flies a La7 which shines below 10K), hunting buffs, eveading buff hunters, picking other alt monkeys, pretending to pick other alt monkeys, and so on...
If you are at 10K and see a con at 30K, you have much less to worry as if he was at 12K. If he attacks you, 9 of 10 times he will be way too fast for any successful attack
Conclusion: Fly what you like, when you like, and where you like. Don't worry to much about other people.