I think of domains as being somewhat like little restaurants...it is perfectly fine to not be able to afford a place in Londons Mayfair or NY Time Square, very few can have a killer keyword in .com with perfect spelling...
The issues come when you are expecting to get high prices for what is in effect crap...
If you have a mistake with your address on Mayfair it is quickly rectified and people still come, if you have a problem with your address in a random back alley that no one can find you are screwed.
Think of a mall, a shop represented in there is a .com and outside are all the .nets, right next to the mall being the good keywords in prime locations and they can be found easily; they may not be top tier enough to get into the mall but they can be really easily found where people logically expect them to be...your domain is somewhere about 15 miles down the road behind a dumpster station because of the lack of quality to the keywords.
Anything less than .com gets no type in traffic as a rule, typo domains get far less traffic than the main keywords for every permutation...so I am confused as to why someone might think a typo domain on a sub-extension might be worth anything over reg-fee?
Typo domains are only ever worth what they bring in with revenue, hence...no revenue = no value
