That link looks like a generic trade-in program for Best Buy, not something specific to Surface (no mention of Surface anywhere). Microsoft has essentially the same thing, probably many other stores. As for the actual calculator:
Item: Microsoft Surface Pro 10.6 128GB Windows 8 Black (9UR-00001)
SKU : 7952262
Model: 9UR-00001
What's this item worth?
Best Estimate: $350.00
Good
$350.00
Fair
$245.00
Poor
$157.50
Not Working
$0.00
Item: Microsoft Surface Pro 10.6 64GB Windows 8 Black (9SR-00001)
SKU : 7952226
Model: 9SR-00001
What's this item worth?
Best Estimate: $315.00
Good
$315.00
Fair
$220.50
Poor
$141.75
Not Working
$0.00
Item: Microsoft Surface RT 10.6 64GB Windows 8 Black (7ZR-00001)
SKU : 7979401
Model: 7ZR-00001
What's this item worth?
Best Estimate: $175.00
Good
$175.00
Fair
$122.50
Poor
$78.75
Not Working
$0.00
Item: Microsoft Surface RT 10.6 32GB Windows 8 Black (7XR-00001)
SKU : 7411049
Model: 7XR-00001
What's this item worth?
Best Estimate: $150.00
Good
$150.00
Fair
$105.00
Poor
$67.50
Not Working
$0.00
Now compare to some completed (sold)
eBay listings for the lowest spec, Surface RT 32GB:
The ones that sold October 11 averaged
$290, varying between totally busted up to "brand new," some with Touch cover and some without. When the bare tablet could be sold on
eBay for just under $300 right now, clearly the trade-in programs--including Microsoft's own--are rip-offs.
That's not even mentioning that the lowest spec Pro v1 is still getting around $600-700 average on
eBay.