Cruz del Sur bus from Lima to Tacna, Peru

Eat your heart out, Greyhound.  The highest end buses are either Scania or Volvo 8x2 double deckers.  The 18 hour trip costs approximately 51 USD.

Among the amenities:

• 12 seats downstairs, 27 upstairs.
• Seats recline 160 degrees.
• GPS monitor (just like airliners).
• 3 meals a day.
• 2 restrooms.
• Bingo games.

Site.