(Yes, nada, nix, nothing to pay. The idea is that Cuban doctors provide medical care for Venezuela's poor in return. I hope they get really excellent health car.
As you know, I give lots of time away for free, but it's my time. Nice that Mr Chavez gives away things other people worked for.)
Update - Since President Hugo Chavez's death, Venezuelan opposition leader Henrique Capriles says he would stop trading oil to Cuba for such services as it does not benefit Venezuala.