If you still own a Surface RT and/or a Surface 2 in good working condition, and you live in the US, you can get up to $150 off a new Surface 3. Microsoft is currently running a promotion that offers those users an online code that can be used for a discount for the Surface 3 if they trade in their older model.
The trade-in deal starts with a website where owners of the Surface RT and Surface 2 fill out a form, which will determine the amount they will receive through the promo code based on the condition of their tablet. Here is what's needed to be eligible:
"To be eligible for trade-in, product must power on battery must hold charge and not be required to be plugged in to operate, and be in fully functional, working condition without broken/missing components, cracked display/housing, liquid damage, modification(s) or have device warranty seal broken to be considered working. Cannot be password protected, and include original chargers/accessories. Any appraised value will be determined at trade-in and provided as a Microsoft online store redemption code and is valid online only.
Owners must trade in their older tablet by May 31 and the online redemption code that they receive must be used by June 30.