>> some 4 number .com domains are going for $$$ in auctions!
Yes, I noticed that too. I started picking up some 4 digit numbers about 8 months ago and very few cost more than $30 at that time.
Like biggedon, I think that this sort of domain has the potential for increase in value in the future.
For a sale to an end user, I would expect at least $150 to US$200 each. To get a quick sale, you might not get much more than $50 to $100 each.