The best way to travel in world class comfort and security from the airport to major centres like Sandton, Rosebank, and the CBD, is to take the Gautrain. A quick transfer from the airport for just over R120 delivers you to central Sandton near several international hotels and local star properties. Hotel shuttles for several properties deliver you from the entrance to the Sandton station directly to your hotel, even if it is a block away. (Safe to walk in the daytime, don't in the evening to be extra careful).
Johannesburg can be a scary place for first timers, sure if you're staying in a five star hotel you can probably arrange a hotel transfer from the airport, and you can probably rely on some 'same old' package deal trips in and around Joburg, but if you want to save cash and make friends at the same time speak to Jay or Oupa. Over the years they've proven to be very reliable. So if you want a friendly face to meet you at the airport, or to show you around Soweto, or drive you to the Kruger Park, these are your guys. I use them for colleagues, family and friends and they've never let me down. I'm pretty sure they'll beat any quotes you get on transport, just negotiate. Jay Cel +2783 485 2141 or Oupa Cel +2782 852 2365. Or VTmail me and I'll get in touch with them for you.
If not for the fact that the airport transfer is provided for when I booked the hotel via Internet, I would have to fork out US$30 for a 1 way trip for the airport bus. Mind you the trip is just about 30 minutes and a taxi would have cost much more.
Even in Japan and London you don't see such prices. Please make sure the airport transfer is included when you book your hotel. One way transfer is equivalent to 1 night's stay.