According to an article in the Havana Times [havanatimes.org] the average salary in Cuba (as of 2012) was ~$22 based on a report released by the Cuban government.
Then I would say it is considerably up from what Cubans told me it was ... but, I'll take it on face value since it's not completely out of whack.
The tourism industry is also likely to see a lot of growth.
The Cuban tourism indust already represents about 60% of GDP, and has done so for a long time. A lot of their infrastructure is more or less at capacity, and isn't going to scale well.
Last I was there, they'd doubled the size of the Juan Gomez airport in Varadero ... and they were so over-run that the airport had been reduced to pure chaos -- they had dozens more flights than they could handle. And the resorts themselves didn't know when they were getting huge influxes of people and were unprepared for it. So all of a sudden they had a few hundred people showing up and no rooms for them.
The nice thing about Tourism as an industry is that scale only relates to demand (see winter vs summer demand in Florida as an example of how this already works). Too many tourists? Double the room rates. Double the restaurant prices. Double the airfare. No, triple it! A new horde of US tourists surging demand in Cuba will just drive up prices. Even crappy hotels have no problem accommodating for supply vs demand by racing up the price curve.