i dont agree with reg fee and low XX. I have sold similar names for low XXX in some cases
I personally think they will be worth high XX at least. They are brandable, pronouncable (a rarething in 4 letter .coms nowadays) and very usable IMHO.
Although these domains are hard to find, there are still many like this avaliable to reg. Thats what I based my appraisal on. However, once all LLLL.com's have been regged - these will be worth high XX to low XXX.
I would say around mid $xx as they are at the moment. However when more LLLL.com domains start to go, you will be able to get a much better price for them. Probably low-mid $xxx quite easily.