When they all were taken mainly by domainers they were going crazy that they'd be the new LLL.com's where the prices went from $xxx to $xx,xxx in a very short period of time.
However, what has happened with LLLL.com's is that they went very quickly to $xxx but have since dropped considerably so you can acquire LLLL.com's (4 letter.com's) from $15 upwards although if you want a really nice LLLL.com such as Made, Ball etc then those prices are different regardless of it being an LLLL or not.
Just have a look on Domainer forums such as Namepros, DNF, DigitalPoint etc and you can find some really cheap.
And you can get them for cheap. Got one .com as recently as last year, with the .org as a freebie. I'm now considering selling my 3 letters/numbers domain name - .net and .org.