Now, T-Mobile's pre-paid service has sold out of the phone, which was priced at $199.99 with no contract. At that price T-Mobile was charging more than the $129.88 that Walmart tagged the phone at, and the $149.95 that the Lumia 521 was offered for on HSN. The latter also threw in a screen protector and a car charger.
There is no word when the phone will be back in stock for Walmart or T-Mobile, or when HSN will put the phone back up for sale.
source: T-Mobile via WMPoweruser