I hadn't heard of that either (until now)... someone just told me that the Havana office charges a fee for the interview.
At first I wasn't surprised since it's commonplace in Cuba for them to charge something for most services (leave it to the Cubans lol!)... but this is the Visa office so we're dealing with Canadians, not Cubans. I'm having a hard time beleiving this! Gotta do some research!