Interns salaries have been paid already.
On the issue of registrars, these doctors (yes, they are already doctors) give their services to KNH. You can argue that its "training", in actual sense, they run the hospital. The journey to become a specialist is a gruelling 11 years. They need to be paid for providing expert services to the givt (KNH).
As a country, we have a huge shortfall in terms of doctors. We have very few specialists, and the situation will remain the same for, its time to change some of these policies to grow the country. The government can even tie them for a number of years after training them - a tie in clause in their contracts would suffice.