There seems to be a lot of unlicensed radio stations in the area - why?

This recent posting got me thinking.

i know there are numerous non-commercial stations due to a large density of universities; but, according to http://www.bamlog.com/bostonlp2013.htm there seems to be a plethora of unlicensed pirate stations. many of them in French-Kreyòl or other English-Caribbean.

Some of my favorite stations i just found out a few years ago are actually pirate. Is obtaining a valid FCC. license prohibitively expensive or maybe immigants (i'm Haitian-American by the way) don't know of federal procedures due to language/cultural barriers?