That's doesn't match what I've learned...
Within 14 days: Return phone for a full refund, account set back to how it was before you got the phone, all upgrades, etc., that were available are available again. No restocking fee (VZW has a restocking fee). Or you could return it and get another phone.
After 14 days, up to 90 days: Exchange for any other phone that Costco has, pay the difference in price, if any, between the two phones. E.g., we paid $149 for the X2, if we returned it in a month or two for another phone that costs $199, we'd pay the $50 difference. (Only down-side is that Costco doesn't get all the phones that VZW has in-store.)
Of course, if you cancel service you'll pay early termination...
I've verified this w/multiple employees at the Costco phone kiosk in two local CostCos. The receipt we got from Costco also clearly states a 90 day return on cellular phones as well.