The sad part about being a mobile customer, at least in the US, is that you almost never get the same perks when upgrading your phone with your current carrier, compared to switching to a new one. For example, if you're an existing T-Mobile customer, you will need to shell out $200 if you upgrade with T-Mobile, Amazon, or even Wirefly.
Thankfully, we were just tipped off about a deal in Costco that offers the G2 for $99.99 to both new and existing customers renewing their contracts as well as those adding a new line. There is only one difference - existing customers pay $149.99 and send in a $50 mail-in rebate instead of getting the $99.99 price right off the bat.
The deal is available both online and in-store. Thanks, Mitchell!