Could I get discount for buying MacBook Air?

Generally, there are 3 ways to purchase a discounted Mac.

Through Apple: (two ways)

1) Apple's Recycling program. Gives you Apple Store credit for your old Apple devices.

Details: http://www.apple.com/recycling/gift-card/

2) Student/faculty discount (Education program). The products themselves are discounted, and during a specified "back to school" season, bonus items are given with some purchases. Details: here http://www.apple.com/shop/browse/campaigns/education_pricing and here: http://www.apple.com/us-hed/shop

I believe you can combine both of the above, as well.

Not through Apple:

3) Buy from an authorized re-seller who may be offering discounted or promotional savings. Most re sellers sell at a slight discount, and have occasional sales prices. (i.e. Best Buy, MacConnection, MacMall, etc)