While LLL.coms and pronouncable LLLL.coms have a general ballpark value, I wouldn't say the same about the examples you've given. I've seen more threads where people are looking to buy pronouncable LLLL.nets, but not sure if there is any kind of particular set values yet. They are becoming more and more popular though.
I'd probably stick to LLLL.com and .net for now. LLLL.mobi maybe, I'm not a big fan of .mobi though. The NNNN examples.. I honestly have no clue.