gaaaaa. greyhound not cheap. 
always look for the smaller bus companies with very crazy bus timings like 7am in the morning. can be half the price of greyhound. 
If U are talking about North America travel, almost all smaller bus companies have been bought over by Greyhound.
Unless U are in big cities with lots of asian, you might be able to find Chinese Coach.
For greyhound, Book early like 7 days ahead the price is always cheaper. like 50% of the price when U buy it over the counter for today travel.