Is it worth buying a used defective ps3 for $140.00 or buying a brand new one for $400.00?

May be...

I bought a defective ps3 that was returned to the store for 140.00 and the warrenty seal is still intact. I didnt get it yet but i was wondering if it was worth buying it, and if I should send it to sony for repair or to try and fix it myself, or was i better off just buying a brand new one for more than triple the price? (Its a 40GB version BTW)

see ow much it costs to get it repaired if thats a fair price do it just get it to work somehow and if not use the warranty

First of all stores aren't supposed to sell defective items, you must mean refurbished yes? If not don't buy a defective system, if it's refurbished and it's 140.00 buy it but not defective.

Buy the used model if it works. If you can buy an optional service plan, do so. Most of those are just swap-out if the unit fails during the duration of the coverage.