Find likely cheaper ways to buy a Mac, Dell, or other computer than just walking into an Apple Store, BestBuy, etc.
Apple products, including Macs
Buying using your Cornell-based email address gets you access to Apple's education discount:
Above link from <http://www.dfa.cornell.edu/procurement/supplierlist/computers/desktops-laptops/apple.cfm>, July 20, 2015.
Expect the same pricing as one get's at Apple's own Education store:
Recommend getting AppleCare, repairs are often needed and expensive.
Microsoft Windows-based products
Dell
For the cheapest Dell purchase, consider using Dell Outlet or "refurbished" offerings, which include a 3 year warranty:
Or buy brand new through Cornell to afford you a negotiated discount, but specials you find on your own can sometimes be better deals:
Above link from <http://www.dfa.cornell.edu/procurement/supplierlist/computers/desktops-laptops/dell.cfm>, July 20, 2015.