They're probably going indentured to someone or to an organization that they'll be paying off for a decade or so.
My cousin payed someone to get a work visa to Canada from North Africa, which cost about $15k. Although the first time she did it it was a scam and she lost all of that money, which was pretty devastating for her. Another cousin payed a coyote to get him to Europe (via Greece), and that was cheaper, but they also left the boat for dead in the Mediterranean and he ended up getting deported back to North Africa.
So yeah, $72k is a lot, but if you're desperate and it's not all upfront, I can see it happening.
The person that cleans my house from time to time is undocumented, for example, but she declares income and pays taxes.