I took a bus, but I did it in chunks.
Bus 1) Retiro to Rosario (45 minute to an hour delay because we had to detour around the city due to a huelga) Spent one night in Rosario
Bus 2) Overnight bus from Rosario to Tucuman (about 12 hours... maybe more) Spent one night in Tucuman and left my computer cable in the hostel common room during the commotion caused when a guy had an epileptic seizure on a hard tile floor.
Bus 3) Day trip from Tucuman to Tafí de Valle (roughly 3 hour trip scenic route takes you out of Tucuman and into hills and winding roads) Stayed for about 6 hours before moving on
Bus 4) Another short trip (about 3 or 4 hours) from Tafí de Valle to Cafayate (wine country) in Salta Province. Spent two night in Cafayate seeing bodegas as well as the original (reproduced) Quilmes ruins
Bus 5) Final trip from Cafayate into the city of Salta (about 4 hours with stop for empanadas & baños)... would probably be about 2 hours in a car. Stayed in the city of Salta long enough to get some sleep and then rent a car to see the north.
RETURN:
Clarín's Sunday propeller plane. It's the only plane out of Salta airport in the morning on Sunday's. There are about 16 seats (or less) and only one seat on each side of the aisle. Walking to board the thing felt like the scene in the movie "Almost Famous" when they leave the bus (a.k.a. "Doris") behind and take to the skies. The, when we were descending into Aeroparque Newberry in clouds as thick as pea soup and were getting bounced around, I thought of "Almost Famous" again... but no one started making confessions.
I have no idea how much the buses cost and that was 3 years ago, so it wouldn't matter anyway. We always went FULL-CAMA when possible. (Of course I would go for the complete lie-down option if that were possible over Full-Cama.)
suerte
PS- The thing about taking buses is that usually you travel overnight. And when you do this, you don't usually see the countryside. So it kind of defeats the purpose of the not flying in this case.